Scanner

A virus detection program that searches for viruses. See Also: Anti-virus Software, On-demand Scanner, On-Access Scanner

Sector Viruses

See: Boot Sector Infector, Master Boot, Sector Viruses

Self-encrypting Virus

Self-encrypting viruses attempt to conceal themselves from anti-virus programs. Most anti-virus programs attempt to find viruses by looking for certain patterns of code (known as virus signatures) that are unique to each virus. Self-encrypting viruses encrypt these text strings differently with each infection to avoid detection. See Self-garbling Virus, Encrypted Virus

Self-extracting Files

A self-extracting file decompresses part of itself into one or more parts when executed. Software authors and others often use this file type to transmit files and software via the Internet since the compressed files conserve disk space and reduce download time. Some anti-virus products may not search self-extracting file components. To scan these components, you must first extract the files and then scan them.

Self-garbling Viruses

A self-garbling virus attempts to hide from anti-virus software by garbling its own code. When these viruses spread, they change the way their code is encoded so anti-virus software cannot find them. A small portion of the virus code decodes the garbled code when activated. See Also: Self-encrypting Virus, Polymorphic Virus

Shared Drive

A disk drive available to other computers on the network. Shared drives use the Universal Naming Convention to differentiate themselves from other drives. See Also: Mapped Drives, UNC

Shareware

Software distributed for evaluation without cost, but that requires payment to the author for full rights. If, after trying the software, you do not intend to use it, you simply delete it. Using unregistered shareware beyond the evaluation period is pirating.

Signature

A search pattern, often a simple string of characters or bytes, expected to be found in every instance of a particular virus. Usually, different viruses have different signatures. Anti-virus scanners use signatures to locate specific viruses. Also: Virus Signatures

Slow Infector

Slow infectors are active in memory and only infect new or modified files. See Also: Fast Infector

SMTP

Simple Mail Transport Protocol. The Internet e-mail delivery format for transmitting e-mail messages between servers.

Sniffer

A software program that monitors network traffic. Hackers use sniffers to capture data transmitted via a network.

Sparse Infector

A sparse infector viruses use conditions before infecting files. Examples include files infected only on the 10th execution or files that have a maximum size of 128kb. These viruses use the conditions to infect less often and therefore avoid detection. Also: Sparse Virus

Stealth Virus

Stealth viruses attempt to conceal their presence from anti-virus software. Many stealth viruses intercept disk-access requests, so when an anti-virus application tries to read files or boot sectors to find the virus, the virus feeds the program a "clean" image of the requested item. Other viruses hide the actual size of an infected file and display the size of the file before infection. Stealth viruses must be running to exhibit their stealth qualities. Also: Interrupt Interceptors

System Boot Record

See: Boot Record