example of why you should not rely on unsigned programs. screen from vmware
See the part: "Gen:Heur" - the detection was not manually added by an analyst who believes that Xvirus Personal Firewall is malicious, however they have a generic signature (based on the bytes in the executable) which triggered the detection, which is done to help detect malware they have not yet seen.
Xvirus Personal Firewall is obviously known to Emsisoft, even two employees from Emsisoft are on this forum... Plus, if any Xvirus products were really not clean then it wouldn't be allowed on this forum, period.
Digital signatures are not an indicator as to whether a program is clean or not, it's there to help prevent people from pretending to provide software while claiming it's owned by someone who it isn't owned by. For example, if you made a fake version of Avast, then we would know it's not the genuine version just by checking the digital signature (unless the Avast certificate had been stolen and then used of course). It's essentially verification for the owner of the software - if you downloaded Xvirus Personal Firewall from the official website then you know it's the genuine copy, since the website was not breached and then hijacked by an attacker... Even then, you can do hash checksum checks to make sure it's the genuine copy.
You can rely on unsigned programs, it isn't about whether it's digitally signed or not... It's about if the program is genuinely clean or not. FP detection's happen all the time, not always with non-digitally-signed software, it's a natural thing with security software...