After latest update, Avast says tor's firefox.exe has IDP.Generic virus/trojan. Does it? How can I be sure it doesn't?
Well, using antivirus when using Tor is a bad practice - but if you need this(sometimes it has it's uses and the problems AV makes are counterweighted by the tasks it solves) - use a proper antivirus. I do not recommend using Avas, Eset(NOD32 and other crap from them), Kaspersky(it spies on you in open, it's a malware, not antivirus), Symantec and Panda. What I do recommend is BitDefender and Sophos(enterprise version). But only if you really need it and you know what you're doing!