In computing, stealth refers to an event, object, or file that evades methodical attempts to find it. In particular, the term applies to certain computer viruses, and to a state of affairs in which a computer or port is rendered invisible to hacking programs.
A stealth virus can pass through an antivirus program unless and until the program is updated to include the virus in its database. Such a virus can infect the boot sector of a diskette, removable disk, or hard drive, thereby copying itself onto other media when files or folders are opened or transferred. If such a virus is written and distributed with malicious intent, it can cause great damage to computers and networks. The problem is especially serious if the virus does its dirty work insidiously, so it is not even discovered until it has spread to thousands of computers and corrupted millions of files.
Hackers are constantly scanning the Internet for computers or networks to exploit. An effective firewall can keep hackers out of computers, and is considered a must for computers equipped with broadband, always-on Internet connections. The best firewalls keep hacking programs from detecting the existence of a computer or network port. When a port-scanning program encounters a stealth (invisible) port, no reply is received in response to requests for connection. The hacking program then passes on to the next potential victim.