FreeBSD has acknowledged a security issue, which can be exploited by malicious people to conduct brute force attacks.

The security issue is caused due to the "arc4random()" function using insufficiently random entropy sources within the first 5 minutes after starting the boot process or until collecting enough random data. This weakens applications and processes relying on the security of "arc4random()" (e.g. when creating IVs for WEP, creating IP packet identifiers, kernel RPC transaction identifiers, and within GEOM ELI and GEOM shsec providers).

Solution
Update FreeBSD or apply patches.
Further details available to Secunia VIM customers

Provided and/or discovered by
The vendor credits Robert Woolley, Mark Murray, Maxim Dounin, and Ruslan Ermilov.

Original Advisory
FreeBSD-SA-08.11.arc4random:
http://security.freebsd.org/advisories/FreeBSD-SA-08:11.arc4random.asc

Deep Links
Links available to Secunia VIM customers