Backdoor:W32/Tofsee silently uses the user's machine to send out spam emails and messages, mine for virtual currency and perform other malicious activities, as directed via instructions from a remote server.
Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.
Backdoor:W32/Tofsee may be found being offered on websites, or dropped on the user's machine as part of the payload of another malware. Tofsee's executable file is distributed with a Flash Player icon, as a decoy to lure the unsuspecting user into clicking it and launching the malware.
When Tofsee is executed, it first creates a copy of itself in the following location:
And creates the following registry key to make sure this copy is executed each time the computer is started up:
Next, the malware creates and runs a new thread in the 'svchost.exe' process and adds itself as a 'trusted program' to the Windows Firewall. Finally, it deletes the original executable file to cover its own tracks.
Once Tofsee has added itself as a trusted program, it can safely communicate with a remote Command and Control (C&C) server to obtain additional instructions, as well as download several plug-ins or modules that it loads into memory. These allow the malware to:
And so on, as per directions received from the C&C server.
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