Disclosed are a computer system, a signature verification server, a method of supporting signature verification by a computer system, and a method of verifying signature. Embodiments of the present disclosure relates to a technology of misdiagnosis verification of signature used for a malicious code diagnosis, and more particularly to technologies which derive a result of performance of a malicious code diagnosis simulation on signature in a multi-user computer environment to use an actual client antivirus software and thus can overcome physical, spatial, and temporal limitations of conventional signature misdiagnosis verification by pre-distributing preliminary application signature in a state where misdiagnosis verification has not been completed to a plurality of user computers to reflect the preliminary application signature to a malicious code diagnosis on files stored in the plurality of user computers and performing misdiagnosis verification on the preliminary application signature based on information collected in connection with a result of the diagnosis.