Since multiple implementations of SSH are available, one might wonder which distribution to choose.

OpenSSH is the most widely used version of SSH today. It is the default SSH client and server for all major Linux distributions and BSD variants, and it is available for many proprietary Unix flavors as well. SSH Communications makes a version of SSH that can be used under Linux, FreeBSD, NetBSD and OpenBSD for non-commercial use, but unlike OpenSSH, the software is not freely distributable.

Despite this drawback, Bob Toxen, one of the original Berkeley Unix programmers, recommends that administrators use the SSH client and server produced by SSH Communications Security. "I strongly recommend that version over OpenSSH," he told NewsFactor. "There's about a four-to-one ratio in terms of bugs. There are serious problems with OpenSSH."