Category: Malware

Type: -

Aliases: Oporto, Win32_Oporto, Win32.Oporto


Oporto is a Windows virus. It stays in memory only until the host process (infected program process) terminates. The virus infects PE (Portable Executable) files, the infection is of appending type. Upon infection the virus increases the size of the last file section, writes its code there and modifies necessary fields in PE header (affected section characteristics). To get control when an infected file is run, the virus replaces first bytes of program's startup code with a short routine that passes control to virus body. With this trick the virus doesn't have to modify program's entry point address. Before the virus passes control to the host program the replaced area is restored.


Automatic action

Based on the settings of your F-Secure security product, it will either automatically delete, quarantine or rename the detected program or file, or ask you for a desired action.

Knowledge Base

Find the latest advice in our Community Knowledge Base.

About the product

See the manual for your F-Secure product on the Help Center.

Contact Support

Chat with or call an expert for help.

Submit a sample

Submit a file or URL for further analysis.

Technical Details

When an infected file is run, the virus searches for PE EXE files in current directory, then in Windows or Windows system directories, and infects these files. Then the virus hooks up to 15 Windows file access functions (file searching, opening, etc.) and stays in Windows memory as a part of host program. When hooked functions are accessed the virus searches for more PE EXE files on the disk and infects them.

The virus is able to hook Windows functions only in case the host program uses them (the program has imports of these functions from Windows kernel). The 'life-time' of the resident virus copy fully depends on the life-time of the host program: when it is terminated, the resident virus code is terminated too.

The virus has a payload: it deletes anti-virus data file ANTI-VIR.DAT if found. On 24th of September the virus displays a MessageBox and halts the system: