Thanks to all who replied to my request, although it seems I didn't quite make it clear what I was looking for. I'm not particularly interested in a strong cryptographic solution, as this isn't intended to detect intentional tampering - just unintentional, such as a bad spot on a hard drive or corruption. Turns out that Simtel has a couple of such packages in /SimTel/msdos/virus - CVIRPROT.ZIP is enough protection, although STEALTH.ZIP looked intriguing... I was, however, interested in what Fred Cohen said about there being a generic attack against such methods when applied to software protection against viruses (virii?). Is there such a generic attack, besides the obvious of jumping around the detection code? How about encrypting the executable, adding loader and decryption code, then decrypting the executable at runtime - would that defeat such an attack, or all such defenses doomed to failure? -- Ed Carp, N7EKG Ed.Carp@linux.org, ecarp@netcom.com 214/993-3935 voicemail/digital pager Finger ecarp@netcom.com for PGP 2.5 public key an88744@anon.penet.fi "Past the wounds of childhood, past the fallen dreams and the broken families, through the hurt and the loss and the agony only the night ever hears, is a waiting soul. Patient, permanent, abundant, it opens its infinite heart and asks only one thing of you ... 'Remember who it is you really are.'" -- "Losing Your Mind", Karen Alexander and Rick Boyes