Method and system for protection against information stealing software

Methods and systems reduce exposure to a dictionary attack while verifying whether data transmitted over a computer network is a password. In one aspect, a method includes performing a search of network traffic based, at least in part, on a weak validation using a Bloom filter based on an organizational password file, determining the existence of a password in the network traffic based only on the weak validation, and determining whether to block, alert, or quarantine the network traffic based at least in part on the existence of the password in the network traffic.