I’ve modified termsrv.dll 5.1.2600.2055 (xpsp_sp2_beta1.031215-1745). AVAST find Win32:Trojan-gen {other} in this file and moved it to vault. After next virus base upgrade AVAST didn’t do that. What happened?
The avast Win32:Trojan-gen is generic signature (the -gen at the end of the malware name), so that is trying to catch multiple variants of the same type of malware and is a fine balance between detecting a new variant and detecting something valid as infected.
So as this signature is tweaked to reduce false detections some files previously detected may no longer be detected. A very good reason never to delete files but to send them to the chest, especially if it was detected by a generic signature.