What is Stealth Virus

A stealth virus is a hidden computer virus that attacks operating system processes and averts typical anti-virus or anti-malware scans. Stealth viruses hide in files, partitions and boot sectors and are adept at deliberately avoiding detection.

These viruses use certain techniques to avoid detection. They may either redirect the disk head to read another sector instead of the one in which they reside or they may alter the reading of the infected file’s size shown in the directory listing. For instance, the Whale virus adds 9216 bytes to an infected file; then the virus subtracts the same number of bytes (9216) from the size given in the directory.

This virus is one of rare virus which is Resident,Boot Sector,File infector and sparse TYPE.

Effects of Stealth Viruses

On 22nd Sept of any year, if you get the message “FRODO LIVES” in large letters on the screen, surrounded by a moving pattern, your system is affected by FRODO STEALTH VIRUS.

On January 5 of any year, if the screen turns green and the text “TYPE HAPPY BIRTHDAY JOSHI” is displayed then your system is infected with JOSHI STEALTH VIRUS. The system will not respond until “HAPPY BIRTHDAY JOSHI” is typed.

How Stealth Viruses Infect Computers

kaspersky explains

A stealth virus can infect a computer system in a number of ways: For instance, when a user downloads a malicious email attachment; installs malware masquerading as programs from websites; or uses unverified software infected with malware. Similar to other viruses, it can take over a wide variety of system tasks and can affect the computer’s performance. When performing such tasks, antivirus programs detect the malware, but the stealth virus is designed to actively remain hidden from antivirus programs. It accomplishes this by temporarily moving itself away from the infected file and copying itself to another drive and replacing itself with a clean file. The stealth virus can also avoid detection by concealing the size of the file it has infected.

Protection from Stealth Virus

It is impossible to fully rid oneself of it once infected.You have to completely wipe the computer and rebuild it from scratch to fully eradicate the presence of a stealth virus.

Regularly-updated antivirus software can reduce risk, but antivirus software is also caught in an endless cycle of finding new threats and protecting against them.

Stealth virus eradication requires advanced anti-virus software or a clean system reboot.