Layer Seven Security

The Final Frontier: The Challenges in Developing Secure Custom ABAP Programs

In November, SAP released an unusually high number of Security Notes to patch various forms of injection vulnerabilities in it’s software. The trend continued in December with the release of several patches for code injection flaws in the Computer Center Management System (BC-CCM), Project System (PS-IS),  Transport Organizer (BC-CTS-ORG) and work processes in Application Servers responsible for executing ABAP programs (BC-CST). Given this alarming trend, this article is focused on discussing the challenges of developing secure ABAP programs for SAP systems, free of common vulnerabilities including not only injection flaws, but cross-site scripting errors, buffer overflows, directory traversals and backdoors and rootkits.

There are three attack surfaces in SAP systems. The first is through improperly defined and controlled application-level access. This attack surface is the most commonly known and understood by SAP customers. Today, most SAP clients deploy any one of a variety of access management tools to control access to sensitive functions and maintain a strict segregation of duties in their ERP systems. This manages the risk of unauthorized access through inadequate authorization structures that grant excessive or conflicting privileges to users and administrators.

The second attack surface lies at the platform level. This generally refers to components of the NetWeaver Application Server, also referred to as the Basis area of SAP systems. The NetWeaver AS is the technical foundation of the entire SAP software stack. It provides the runtime environment for SAP applications and includes work processes for ABAP and Java programs, gateways and modules for managing RFC, Web-based and other forms of communication protocols, tools to manage user roles, profiles and authorizations, and utilities that control certain database and operating system functions. The secure configuration and management of the NetWeaver AS is a vital component of a comprehensive SAP security strategy. However, the results of our security assessments repeatedly reveal common vulnerabilities in basis settings in most SAP environments. This provides a lush attack surface to internal and external attackers looking for an avenue to manipulate or appropriate business data or deliberately disrupt the availability of SAP systems.

The third and final attack surface in SAP provides an even greater array of opportunities for attackers. This surface exists at the program level. ERP systems such as SAP are designed to perform thousands of distinct functions ranging from, for example, adding a vendor to a list of approved suppliers, performing a transport to implement a change in a specific system, or encrypting/ decrypting traffic between servers or clients. These functions are performed by programs stored in the database table known as REPOSRC that are called when requested by work processes in the NetWeaver AS.

SAP programs are developed using two distinct programming languages: Advanced Business Application Programming (ABAP) and Java.  Both are vulnerable to coding errors that could expose SAP programs to exploits such as code, OS and SQL injection, cross-site scripting, cross-site request forgery, buffer overflow, directory traversal and denial of service. SAP programs are also susceptible to missing or broken authority-checks that could lead to unauthorized execution of programs. Finally, SAP programs can contain backdoors through hardcoded credentials that bypass regular authentication and authorization controls, as well as malware known as rootkits that provide attackers with remote, privileged access to system functions and resources.

SAP performs a rigorous code review for all standard or delivered programs prior to release. However, some of the vulnerabilities present in the code base are not detected and patched until after release. Security Notes are therefore an important mechanism used by SAP to patch vulnerabilities arising from programming errors.

Custom programs are rarely subject to the same level of scrutiny applied by SAP to standard programs. Programs developed by in-house or off-shore developers to meet the needs of customers not met by standard SAP functionality are often laden with vulnerabilities that, when exploited, undermine the integrity of entire SAP landscapes. Such landscapes are only as strong as their weakest point. A robust application layer fortified with GRC tools has led attackers to shift their focus to the platform and code level. Given the relative openness of most SAP systems at the technical level, the strategy is proving to be profitable.

SAP has responded by issuing a series of recommendations to customers to strengthen configuration settings in components of the NetWeaver AS. These can be found in the whitepaper Secure Configuration of the SAP NetWeaver Application Server Using ABAP.

However, understandably SAP is less vocal on development procedures for custom programs since this is generally the responsibility of each SAP customer. The challenge should not be underestimated. Although manual code reviews to detect common vulnerabilities are theoretically possible, the skill-set to effectively review custom code is not only rare but expensive. Furthermore, it often leads to an increase in development time. Customers should consider investing in code scanning tools that are tuned to detect suspicious statements in ABAP code and integrate directly into the SAP Transport Management System (TMS). Such tools should also be capable of auto-correcting ABAP statements to minimize resource requirements and the impact on existing development times. Presently, the only tool capable of detecting and auto-correcting vulnerabilities in custom ABAP programs, with direct integration with SAP TMS, is Virtual Forge CodeProfiler. To arrange a security scan of custom programs in your SAP environment using CodeProfiler, please contact a representative at Layer Seven Security.

Cybersecurity Disclosures: A Three Step Strategy for Compliance with the New SEC Guidance

Against a background of growing investor concern and pressure from legislators, the Securities and Exchange Commission (SEC) is leading the drive for more open and timely disclosure of cybersecurity risks and incidents from public companies. Earlier this year, it challenged Amazon’s decision not to disclose the financial impact of the theft of customer data held by its subsidiary Zappos in the company’s annual report. In the view of the SEC, Amazon failed to comply with rules incorporated in the Securities Act of 1933 and Securities Exchange Act of 1934 which require “disclosure of timely, comprehensive, and accurate information about risks and events that a reasonable investor would consider important to an investment decision” (SEC). These rules were clarified by the SEC in guidance on disclosure obligations related to cybersecurity risks and incidents, issued in October last year.

The guidance is based on a broad definition of cybersecurity which is seen as a body of technologies, processes and practices designed to protect networks, systems, computers, programs and data from attack, damage or unauthorized access. It includes attacks and breaches caused by both insiders and third parties. Therefore, incidents such as the theft of proprietary software by an employee at Goldman Sachs in 2009 would fall into scope of the disclosure requirements.

According to the guidance, incidents include not just deliberate attacks, but breaches and losses resulting from unintentional events. In addition to attacks designed to misappropriate financial assets and intellectual property or other sensitive information, it includes Denial-of-Service (DoS) attacks targeted at disrupting operations.

The guidance requires public companies to disclose the risk of cyber incidents if these issues are among the most significant factors that make an investment in the company speculative or risky. In order to comply with this requirement, registrants are expected to evaluate the likelihood and impact of a material incident arising from a breach or failure in their information systems and infrastructure. The assessment should take into account factors such as the value of information contained in applications and systems, the degree to which the fiscal health of a company is tied to the confidentiality, integrity and availability of such information and technology in general, known vulnerabilities, prior security incidents, the financial and reputational impact arising from an incident, and the strength of preventative controls. Based on such an evaluation, a company is required to disclose material cybersecurity risks in the 10-K annual report provided to the SEC which is made available to investors and the general public. Such disclosures are often buried within the section related to risk factors in the 10-K. However, registrants are obliged to discuss material risks within the Managements Discussion and Analysis (MD&A), an area more widely read by investors. The SEC provides some leeway on the extent of information registrants should disclose, recognizing that too much disclosure could be exploited by malicious groups and compromise security efforts.

An inventory of mission-critical or information-rich systems within most publically-listed organisations often reveals a suite of SAP applications supporting everything from sales and distribution, purchasing, financial reporting and human resource management, as well as more industry-specific areas. Invariably, these applications are powered by the SAP NetWeaver Application Server (AS), a platform used to develop programs, manage database, operating system and network connections, link together SAP and non-SAP applications, and a myriad of other administrative tasks. The NetWeaver AS is a complex, Web-enabled area of SAP that is vulnerable to a variety of internal and external attacks. These vulnerabilities are widely known and include various forms of injection, cross-site scripting, session hijacking, DoS, and other attacks. Therefore, when reviewing the strength of preventative controls in SAP systems to determine whether there exists a material cybersecurity risk that requires disclosure, companies should closely review the configuration of the NetWeaver AS. Misconfigurations in this area could create vulnerabilities that can be exploited by insiders and outsiders to embezzle assets, leak information including intellectual property, corrupt data or disrupt operations.

Securely configuring the NetWeaver AS should be the first step in a three pronged strategy aimed at managing cybersecurity risks in SAP systems. When combined with appropriate access controls and technical settings at the application level, companies running SAP applications will greatly reduce the likelihood of material risks in their SAP environments that may require disclosure.

SAP has issued a number of recommendations to help customers configure the Netweaver AS. These recommendations can be found in the whitepapers Secure Configuration of SAP NetWeaver Application Server using ABAP and Protecting SAP Applications Based on Java and ABAP Against Common Attacks. They include regular monitoring of the security configuration of the NetWeaver AS which can be met through vulnerability assessments performed by Layer Seven Security. The assessments leverage software certified by SAP and detect over 400 vulnerabilities in components of NetWeaver Application Servers, the foundation of SAP applications. To learn more, visit our services page or call 1-888-995-0993 to connect with one of our SAP security consultants.

SOAP Opera: Securing SAP Web Services

The best run businesses may run SAP but very few run it exclusively. Most SAP systems operate in a complex, heterogeneous environment with information and processes spread across multiple systems including legacy applications. For SAP, this has always been a barrier to the rapid deployment of its software. Traditional solutions such IDocs, BAPIs and other interfaces were far from ideal, requiring extensive manual effort. Creating and managing the interactions between SAP and non-SAP systems was not only difficult and time-consuming, it hindered program development. Minor change requests would lead to long-term projects that would take months and, in some cases, years to implement.

Service-Orientated Architecture (SOA) offered a salvation for SAP. By embracing the principles and techniques of SOA, SAP was able to improve interoperability (which is essentially the ability to integrate diverse systems) and reduce development time and effort. This meant breaking down SAP functions into discrete objects that could be accessed or executed by other applications using open protocols and standards. These objects are known as Web services or, when subject to SAP business logic, Enterprise Services (ES). Examples include the ability to read customer data, create a sales agreement, cancel a shipment or update bank details.

Web services are constructed using standardized rules to support flexibility and ease of integration. The rules include Simple Object Access Protocol (SOAP). The name is misleading. SOAP is neither simple nor a protocol. In fact, it’s a schema for data exchange using Extensible Markup Language (XML). It provides a standardized way to exchange information between diverse systems. SOAP messages are XML documents that consist of an envelope, header and body.

Other Web service rules include Universal Description Discovery Integration (UDDI), which is used to register and catalog Web services, and Web Services Description Language (WSDL), which is equivalent to method signatures in programming language, used to describe how web services are called, the types of data that are transferred, as well as information related to network protocols, addresses and ports. We should also mention Web Services Business Process Execution Language (WS-BPEL), which is used to construct applications by binding together different Web services.

Service orientated environments are based on loosely coupled Web services that locate one another through UDDI registries and then dynamically bind together during runtime. When combined with WSDL, this happens through automated applications without human intervention. It can also be initiated by end users interacting with SOA environments through Portals. Portals, such as the SAP Enterprise Portal (EP), act as proxy agents, enabling users to interact with Web services in a SOA. We will discuss security concerns with the EP in a later article since this review is focused exclusively on Web services.

The SAP NetWeaver Application Server (NetWeaver AS) incorporates a Web Service Framework that includes ABAP and Java runtime environments for SOAP requests, tools that support UDDI registration and an Internet Communication Manager (ICM) to manage Web service calls usually through port 80NN (HTTP). Netweaver AS is the cornerstone of the SAP software stack. It integrates SAP and non-SAP applications and manages connections between the application layer and the underlying operating system and database.

SAP Internet Communication Manager

Creating a Web service in SAP couldn’t be any easier. In most cases, it can be performed through simple wizards in both ABAP (Object Navigator) and Java (Developer Studio). You will need authorizations associated with the role SAP_BC_WEBSERVICE_ADMIN including S_ICF_ADMIN. Transaction WSADMIN is used to manage runtimes, generate WDSL documents and publish Web services in the UDDI.

Securing Web services is a formidable challenge. SOAP was designed for simplicity and extensibility, not security. Standard SOAP messages do not perform any authentication between endpoints or intermediaries, or provide mechanisms to protect the integrity or confidentiality of data at rest and in transit. For the most part, Web services share the same underlying architecture as Web applications. Consequently, they are vulnerable to similar exploits. This includes SQL injection attacks that target databases accessed by Web services, dictionary attacks against password protected Web services, directory traversal, buffer overflows, packet sniffing, man-in-the-middle exploits, schema poisoning, denial-of-service attacks, Trojan horses containing logic bombs, trapdoors and backdoors and XML injection attacks that target Web services directly which could lead to cross-site scripting. Since UDDI directories and WSDL mechanisms rarely require authentication and authorization, Web services are also vulnerable to remote reconnaissance attacks which are used to garner information on target systems to probe for potential vulnerabilities. Specialized search engines such as Shodan simplify the task of fingerprinting Web services that are exposed to the public, making reconnaissance very easy.

Firewall rules can be configured to ensure Web services are only accessed from legitimate networks and trusted systems. This could be supported by Intrusion Prevention Systems (IPS) that monitor for attacks against Web services. However, in reality, network perimeter controls offer scant protection against such attacks. Web services travel over HTTP. This is left open by most firewalls. Furthermore, the typical IPS does not support SOAP. Next-generation firewalls that have the ability to filter HTTP content including XML messages are expensive and offer poor throughput. Therefore, they are rarely adopted by organisations.

XML gateways provide the equivalent level of protection without the degradation in performance.  Gateways are like application-level firewalls that act as intermediaries between external (untrusted) and internal Web services. Since they force SOAP messages to pass through hardened entry points that restrict access based on source, destination and other measures, gateways offer some measure of protection against Web service attacks. Enterprise level appliances such as the Cisco ACE XML Gateway can be integrated into SAP environments.

Gateways are attractive targets for attackers and, if subverted, can compromise internal Web services. Therefore, they should be regularly patched and supported by strong policies and rule-sets. Also, they should be reinforced by other components of an effective defense-in-depth strategy. This should include SSL/ TLS (HTTPS) to authenticate and encrypt SOAP messages when dealing with single endpoints (SSL doesn’t work with SOAP messages that traverse multiple destinations). It should also include adequate header extensions in SOAP messages that define security policies for message handling in accordance with the WS-Policy framework. The policies should include requirements for authentication, encryption and non-repudiation. Digital signatures should be used to protect against unauthorized modification of the policies. They should also be used to protect UDDI entries since compromised entries could lead requestors to bind to malicious Web service providers. Web services and underlying data should be replicated to improve availability and guard against denial of service attacks. Reconnaissance attacks can be blunted by disabling default error messages in the ICM and J2EE that disclose sensitive system information. They can also be thwarted by deactivating the info ICF service which can be abused by remote attackers to retrieve the same information. The presence of the info and dozens of other high-risk SAP services can be detected through vulnerability assessments performed by Layer Seven Security. The assessment leverage SAP-certified software to scan for over 400 security vulnerabilities in SAP systems. This includes services that can be accessed by attackers to perform critical functions and compromise such systems. Some of these services do not require any user authentication.

A Ten Step Guide to Implementing SAP’s New Security Recommendations

On January 16, SAP issued a revamped version of the whitepaper Secure Configuration of SAP Netweaver Application Server using ABAP, which is rapidly becoming the de-facto standard for securing the technical components of SAP. According to SAP, the guidance provided in the whitepaper is intended to help customers protect ABAP systems against unauthorized access within the corporate network. In fact, many of the recommendations can also be used to protect SAP systems against remote attacks originating outside such a network. These attacks are targeted at the technical components of SAP Netweaver that are responsible for managing user authentication, authorization, encryption, passwords and system interfaces, as well as underlying databases and operating systems. Breaches in these components can enable attackers to take complete control of an SAP environment.

The following is a quick guide to help you comply with SAP’s recommendations.

1. Disable unnecessary network ports and services. In most cases, this means blocking all connections between end user networks and ABAP systems other than those required by the Dispatcher (port 32NN), Gateway (33NN), Message Server (36NN) and HTTPS (443NN). NN is a placeholder for your SAP instance number. Administrative access should only be allowed through secure protocols such as SSH and restricted to dedicated subnets or workstations through properly configured firewall rules.

2. Install the latest version of SAP GUI. This should be 7.10 or 7.20 with activated security rules configured with the ‘Customized’ setting and the ‘Ask’ default action.

3. Implement strong password policies, restrict access to password hashes in tables and activate the latest hashing algorithms. SAP does not specify the exact settings for password policy parameters but you should use frameworks such as the PCI DSS as a proxy. Refer to section 8.5 of the standard. Default passwords should be changed for standard users and the password hashing mechanism should be upgraded to the latest version available for your system. Wherever possible, downward-compatible hashes should be removed from the database.

4. Enable SNC and SSL. SAP client and server communication traffic is not cryptographically authenticated or encrypted. Therefore, data transmitted within SAP networks can be intercepted and modified through Man-In-The-Middle attacks. Secure Network Communication (SNC) should be used for mutual authentication and strong encryption. This can be performed natively if both servers and clients run on Windows. You will need to use a third party product to secure connections between heterogeneous environments such as AIX to Windows.

SNC will secure network communication using the SAP DIAG and RFC protocols. For Web-based communication, you should switch to HTTPS/ SSL and restrict access to the relevant cryptographic keys.

5. Restrict ICF services. Many of the services enabled by default in the Internet Communication Framework (ICF) are open to abuse and could enable unauthorized and malicious access to SAP systems and resources. At a very minimum, you should deactivate the dozen or so services mentioned by SAP in the white paper. This can be performed through transaction SICF.

6. Secure Remote Function Calls (RFC). Wherever possible, remove trust relationships between systems with differing security classifications and hardcoded user credentials in RFC destinations. The belief that RFC connections using SAP_ALL privileges is fine as long as the user type is not set to dialog is a myth. This represents a serious risk to the integrity of information in SAP systems.

7. Secure the SAP Gateway. The Gateway is used to manage RFC communications which support SAP interfaces such as BAPI, ALE and IDoc. Access Control Lists (ACL) should be created to prevent the registration of rogue or malicious RFC servers which can lead to the interruption of SAP services and compromise data during transit. You should also enable Gateway logging and disable remote access.

8. Secure the SAP Message Server. The Message Server is primarily a load balancer for SAP network communications. Similar to the Gateway, it has no default ACL which means it is open to the same type of attacks. You should filter access to the Message Server port using a firewall and create an ACL for all required interfaces.

9. Regularly patch SAP systems. Implement missing SAP Security Notes and patch systems at least once a month. Security Notes can be downloaded from the SAP Service Market Place.

10. Regularly monitor the SAP security configuration. Standard SAP services such as EarlyWatch (EWA) and the Computing Center Management System (CCMS) can be used to monitor some security-relevant configurations. However, they do not provide the same coverage as professional-grade security tools such as those used by Layer Seven Security. You can learn more about SAP security monitoring through vulnerability assessment here. To discover why vulnerability assessments should be an integral component of your SAP security framework, click here.

Netweaver Single Sign-On: Is it Worth the Risk?

SAP’s acquisition of SECUDE in 2011 is finally bearing fruit. Recently, SAP announced the launch of Netweaver Single Sign-On 1.0 which can be downloaded from the Service Marketplace. This is the latest addition to SAP’s identity and access management portfolio and is based on SECUDE’s Secure Login and Enterprise SSO solutions. It uses protocols such as Kerberos, X.509 and SAML to enable mutual authentication between not only SAP applications but between SAP and legacy systems. It also supports cross-company authentication between different domains. This is achieved through federated identity systems based on a choice of IDP or STS, which is used to issue and verify security tokens.

SSO aligns well with SAP’s ambition to ‘help companies run better’.  It does so by seamlessly integrating people, processes and technology without the inconvenience of multiple logons. It also lowers the Total Cost of Ownership (TCO) by reducing the burden on Helpdesks that spend an inordinate amount of time helping locked-out users reset their passwords. According to research performed by the META Group (now owned by Gartner) 20-50% of all support calls are caused by forgotten or expired passwords. The cost to manually reset passwords ranges from $15-30 per call, and on average, users call help desks with a password problem 4 times a year”. Forrester Research estimates the average cost is closer to $70. This should give SAP a leg up over the competition, not that it needs it, judging by the latest results.

For security folks, the case for SSO is less clear cut. While it enables companies to standardize and enforce stricter password policies to legacy systems, simplify administration and reduce the risk that users will write down credentials needed to logon to different systems, SSO has some serious drawbacks.

Firstly, implementing SSO is no picnic. Retrofitting legacy systems can be a nightmare. Secondly, since SSO only deals with authentication and not authorization, the administrative gains are minimal: somebody still has to setup privileges for every new user. Privileges are rarely synchronized between systems.

Thirdly, it creates a single point of attack. This is by far the most serious concern with SSO which delegates authentication to a single, central Identity and Access Management (IAM) system. IAMs are attractive targets for attackers, especially when they provide direct access to information-rich SAP systems. Attack vectors used to compromise SSO logins and passwords range from cross-site scripting, phishing to social engineering and have been successfully deployed against SSO schemes used by tech giants such as Google, Facebook and Twitter. A special mention should be given to Denial of Service (DoS) attacks. Note that SSO intensifies the damage caused by DoS against an IAM since it impacts every system relying upon the IAM for authentication.

Clearly, SSO is a double-edged sword. To realize the benefits, you have to manage the risks. This should include multi-factor authentication and hardening of all systems in the SSO environment. The latter should include regular patching, client-side security such as SNC encryption for SAP GUI traffic and host-level vulnerability assessments. You can learn more about SAP vulnerability management here.

SAP patches a session hijacking vulnerability in the Netweaver Portal

Imagine a system that provides a single, unified interface to all your SAP applications for not only everyone in your company but customers and suppliers. Imagine also that this system is web-based and uses single-sign-on. Congratulations, you’ve just envisioned the Netweaver Portal, the cornerstone of SAP’s strategy to integrate business information and processes and the fountain of much of the company’s recent success. Given its importance, you would think that any security vulnerability in the Portal would be quickly dealt with by SAP’s security engineers. Yet, if this is the case, why did it take SAP one and a half years to patch a vulnerability that left the Portal open to session hijacking?

Session hijacking is also known as session fixation or broken authentication and ranks consistently high in the OWASP Top Ten web application security risks. In fact, in the most recent survey, its rated as the third most prevalent and dangerous vulnerability in web applications. Hijacking occurs when attackers exploit weak functions in the application layer to assume the identities of legitimate users. Attackers usually target passwords, keys, session tokens and other authentication factors. Its not that difficult to find flaws in most applications since developing secure authentication and session management schemes for custom applications is no walk in the park. SAP applications are no different.

In July 2009, SAP was notified about a session fixation flaw in the J2EE engine that affected versions 6.4-7.2 of the Netweaver platform, which is essentially the technical layer of SAP systems. In the words of SAP itself, this flaw could be exploited to gain access to authenticated user sessions (SAP Note 1310561) through attack vectors such as MITM that provide hackers with access to the session IDs of SAP users which can then be used to logon to target SAP systems. The impact can be very high, especially when you consider that the Portal provides Web-based access to HR, financial, customer relationship management, product lifecycle management, and other critical applications (SAP Solution Brief).

The session hijacking vulnerability was eventually patched by SAP through the introduction of JSESSIONMARKID, a secure (HTTPS) cookie that automatically renews after successful logons. However, the shocker was that it took SAP 18 months to develop and release a patch for the vulnerability. That’s twice the length it took the company to rollout its new database, HANA, from “idea to completion” (Vishal Sikka, SAP AG Board member). Its possible that the existence of this vulnerability was well known within hacking communities long before the much anticipated fix was released by SAP. Disclosure guidelines issued by SAP urge security researchers not to publicize information about vulnerabilities until they are patched. Most researchers, rightfully so, choose to follow SAP’s request. However, given the severity of these and other vulnerabilities, customers shouldn’t accept such a long window for patch management. After all, if SAP can develop and release an entirely new database in a mere 9 months, surely it can fix a critical security flaw in its Portal just as quickly.

A Guide to Rootkits and Trojans in ABAP Programs

If you missed Ertunga Arsal’s presentation on SAP Rootkits and Trojans at the 27th Chaos Communication Congress, you can now watch the entire hour-long session below. Ertunga is an accomplished SAP security expert and an entertaining speaker if you appreciate dry, German humour. In this video, Ertunga demonstrates how attackers can use several paths to compromise weak SAP systems (usually development or test environments), infect clients that connect to the compromised systems and then eventually work their way up to production and even partner systems. These so-called˜Triple Penetration’ attacks can compromise entire SAP landscapes.

Ertunga also demonstrates how attackers can crack hashed SAP passwords and discusses problems with SSO. He makes a great comment about how SSO is really a convenience feature and does nothing to improve security and shows how attackers can create their own SSO certificates to logon to SAP using the IDs of users in the target system.

However, the highlight of the session is the discussion around SAP Rootkits and Trojans. Ertunga walks through several injection attacks that can be used to infect ABAP programs. Rootkits can be used to execute commands that, for example, automatically donate part of a company’s profit to charity (the so-called ‘Robin Hood’ worm) or publish salary information online. He points out that development activities should be tightly controlled and monitored, especially if you’re using third party developers with SAP_ALL rights. If your developers are internal, Ertunga warns against hiring developers from competitors since this can open the door to commercial espionage and sabotage.