Stolen Browser Session Cookie Used for Hijack

Darshan Thummar@Mighty

•updated Jun 12, 2026•0•0•6

This rule detects potential session hijacking attempts by monitoring HTTP traffic for unusually long cookie values. Specifically, it looks for HTTP cookies containing base64-like strings (alphanumeric characters, plus, slash, and equals signs) that are 100 characters or longer. A threshold of 5 such occurrences within 3 seconds from the same destination IP address triggers the alert, indicating a possible attempt to use a stolen browser session cookie.