NSA Issues Guidance for Combating Web Shell Malware

Web shell malware, which executes arbitrary instructions on a targeted Web server, is a large and growing cybersecurity problem — and now government intelligence agencies are releasing guidance on how to defend against it. The US National Security Agency (NSA) and the Australian Signals Directorate (ASD) joined forces this week to issue a Cybersecurity Information Sheet on how to detect and mitigate this form of malware.

The sheet includes information on detecting Web shells, such as tips on using known-good comparison, in which a file on the Web server is compared to a "known good" version of the file stored in a secure location.

NSA and ASD also provide instructions on mitigating the threat through the use of IDS/IPS technology, Web flow detection, and file-integrity monitoring to quickly detect files that have been modified without administrator permission.

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