The Cali worm was found on 10th of August 2004. It's a massmailer.
Disinfection & Removal
Allow F-Secure Anti-Virus to disinfect the relevant files.
For more general information on disinfection, please see Removal Instructions.
Cali is packed with Yoda and UPX. It's packed size is 51270 bytes. Once unpacked it grows up to 100KiB.
The executable was compiled with Microsoft's Visual C++ compiler with the stack protection option enabled. It's possible to appreciate in the code this feature, which protects the stack by placing a 'canary' value between the function's local variables and the return address. In this scenario if a buffer overflow would occur, it would be detected before the function returns, making the exploitation of an overflow a non trivial task.
The stack protection is enabled with the /GS option. More documentation on its implementation can be found from "Compiler Security Checks In Depth":
It's worth mentioning that some older worm could be taken over because of a buffer overflow in its networking code. It's interesting that malware writers are also paying attention to security related issues.
Once executed it creates a a mutex named:
in order to avoid being run more than once. And copies itself to:
A registry key will be set to point to the dropped file, the name of the key will be randomly chosen from:
BuildLab RegDone ccApps Microsoft Visual SourceSafe TEXTCONV FriendlyTypeName .Prog WMAudio
therefore, the registry key might look as follows:
[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\] "WMAudio" = "%WinDir%\system\services.exe"
Where %WinDir% is the main Windows folder.
When massmailing, it will attach itself with names such as:
office.exe notes.exe doom3demo.exe resume.exe files.exe request.exe info.exe details.exe result.exe results.exe install.exe setup.exe test.exe google.exe se_files.exe
Detection for Cali worm is available since the following FSAV updates:
Detection Type: PC
Technical Details: Ero Carrera, August 10th, 2004