× Few antiviral products inadequately detect 3proxy as Trojan.Daemonize, Backdoor.Daemonize, etc and many detect 3proxy as a PUA (potentially unwanted program). It may cause browser warning on download page. 3proxy is not trojan or backdoor and contains no functionality except described in documentation. Clear explanation of this fact is given, for example, in Microsoft's article.
3proxy documentation

3proxy documentation

Security recommendations
Optimizing 3proxy for high loads
How To (English, very incomplete)
How To (Russian)
FAQ (English)
FAQ (Russian)

Man pages:
3proxy.8
ftppr.8
icqpr.8
pop3p.8
proxy.8
smtpp.8
socks.8
tcppm.8
udppm.8
3proxy.cfg.3