Threat Description



Aliases: Trojan:​SymbOS/ZeusMitmo.A, Trojan:​SymbOS/ZeusMitmo.A
Category: Malware
Type: Trojan
Platform: SymbOS


When installed on a mobile phone, this trojan monitors all incoming SMS messages and acts as a backdoor for receiving commands sent by an attacker via SMS messages.


Trojan:SymbOS/ZeusMitmo can be manually uninstalled by removing the following program via the phone's Application Manager:

  • Nokia Update

Technical Details

Trojan:SymbOS/ZeusMitmo.A is notable for being specifically designed to steal SMS messages containingm obile transaction authentication number (mTANs), which are like single-use passwords sent by banks to to their account holders' mobile phones to verify online transactions.

This trojan is discussed in the following Labs Weblog post:


ZeusMitmo.A is distributed by Trojan-Spy:W32/Zbot.PUA or Trojan-Spy:W32/Zbot.PUB.

Trojan-Spy:W32/Zbot.PUA sends an SMS message to the user's phone containing a link to a website hosting the malicious ZeusMitmo trojan. If the link is followed, the trojan is promptly downloaded and installed on the phone.

In our analysis, the malicious trojan was a Symbian-signed file for S60 3rd Edition and 5th Edition mobile phones. The file itself is named cert.sis, and may be deceptively billed as a 'Nokia Update'. .jad files, used for Blackberry devices, have also been reported.


During installation, the trojan registers itself to start when the phone is booted up. Once active, the trojan is able to silently monitor all incoming SMS messages.


If an SMS is sent to the user's mobile device with the target bank's authentication code, the malicious software running in the device forwards the SMS to another terminal controlled by the attacker.

The trojan contains a hard-coded phone number for use in sending the stolen SMS messages and receiving commands from the attacker(s).


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