Virus

Spread across programs

• An “Infected” program (or floppy)
• When executed, it copies itself to other places of a system.

  Question: how to write a program that writes itself?

• It may carry an extra “payload” that performs other functions

Boot sector virus

• Modify boot sector of hard drive
• We don't boot drive that much nowadays, so boot-sector virus is largely extinct.

Infected Flash Drive

• autorun.inf in flash drive is honored by many OS systems.

Macro Virus

• Viruses can be written in any sufficiently-powerful language
• Word documents (also Powerpoint presentations and Excel spreadsheets) can thus spread viruses, using Microsoft Macro language.
• Word Macro viruses spread in ordinary business!

E.g Latex Virus

Almost works - but the program can't open file in other directories..

\documentclass{article}
\begin{document}
Foo
\immediate\openout 3 infectedfile.exe
\immediate\write 3{infection}
bar
\end{document}

Virus-Spreading Patterns

• Boot-sector viruses spread in affinity groups -- floppies were a normal means of communication before networks.
• Program viruses spread by people sharing software, often improper or illegal.

First Virus

• A boot-sector virus written by a 15-year-old.

Zero Virus

A zero-day virus (also known as zero-day malware or next-generation malware) is a previously unknown computer virus or other malware for which specific antivirus software signatures are not yet available.