1) Trojan horse 
[malware] Trojan:Win32/FakeSysdef, originally dispersed as an application called `HDD Defragmenter` hence the name `FakeSysdef` or `Fake System Defragmenter`, is a Computer Trojan type of computer virus targeting the Microsoft Windows operating system that was first documented in late 2010. Win32/FakeSysdef manifests as one or more of an ar...