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Panda Protection

Virus Encyclopedia

Welcome to the Virus Encyclopedia of Panda Security.

Mastof.A

Threat LevelHigh threatDamageSevereDistributionNot widespread
Common name:Mastof.A
Technical name:Trj/Mastof.A
Threat level:Medium
Type:Trojan
Subtype: Password Stealer
Effects:  

It is a generic detection for Trojans created using Constructor/Mastof. These Trojans steal the password for the service Yahoo Messenger.

Affected platforms:

Windows 2003/XP/2000/NT/ME/98/95

First detected on:Dec. 21, 2004
Detection updated on:June 20, 2005
StatisticsNo
Proactive protection:
Yes, using TruPrevent Technologies

Brief Description 

    

Mastof.A is not a specific Trojan, but a generic detection for Trojans created using the virus constructor called Constructor/Mastof. These Trojans steal the affected user's password for the instant messaging program Yahoo Messenger.

All the Trojans detected as Mastof.A share the following characteristics:

  • They go memory resident.
  • They send the stolen password to a Yahoo mail account of the author's choice.

Additionally, there are several optional payloads that could be included in Mastof.A, such as disabling the Task Manager and Windows Registry, sending the IP address and version of the operating system of the affected computer, etc.

Visible Symptoms 

    

Mastof.A is difficult to recognize, as it does not display any messages or warnings that indicate it has reached the computer.

However, some of the Trojans detected as Mastof.A display the following fake error message on screen when they are run:

where %Text_String_1% and %Text_String_2% stand for text strings of the author's choice.