Improving Web Application Security: Threats and - CGISecurity

Chapter 2: Threats and Countermeasures 23Arbitrary Code ExecutionIf an attacker can execute malicious code on your server, the attacker can eithercompromise server resources or mount further attacks against downstream systems.The risks posed by arbitrary code execution increase if the server process underwhich the attacker’s code runs is over-privileged. Common vulnerabilities includeweak IID configuration and unpatched servers that allow path traversal and bufferoverflow attacks, both of which can lead to arbitrary code execution.Countermeasures to help prevent arbitrary code execution include:● Configure IIS to reject URLs with “../” to prevent path traversal.● Lock down system commands and utilities with restricted ACLs.● Stay current with patches and updates to ensure that newly discovered bufferoverflows are speedily patched.Unauthorized AccessInadequate access controls could allow an unauthorized user to access restrictedinformation or perform restricted operations. Common vulnerabilities include weakIIS Web access controls, including Web permissions and weak NTFS permissions.Countermeasures to help prevent unauthorized access include:● Configure secure Web permissions.● Lock down files and folders with restricted NTFS permissions.● Use .NET Framework access control mechanisms within your ASP.NETapplications, including URL authorization and principal permission demands.Application Threats and CountermeasuresA good way to analyze application-level threats is to organize them by applicationvulnerability category. The various categories used in the subsequent sections of thischapter and throughout the guide, together with the main threats to your application,are summarized in Table 2.2.