Mar 27, 2026 - For details about updated CVE-2025-53521 (BIG-IP APM vulnerability), refer to K000156741.

Forum Discussion

Antonio3's avatar
Antonio3
Icon for Altocumulus rankAltocumulus
Mar 27, 2026

block a specific user

Hi everyone, Is it possible to create a signature to block a specific user from authenticating to a web portal?   thanks     Antonio
security
Jmtaylor's avatar
Jmtaylor
Icon for Moderator rankModerator
Mar 27, 2026

Antonio3​ 
Yes, this is possible using BIG-IP ASM/Advanced WAF custom attack signatures. The approach is to match the specific username value submitted in the login request (e.g., in a POST body parameter, cookie, or header) and block it.
 Let us know if you need more information