First DOS-based malware celebrates silver jubilee

From Brain to zombie hordes in 25 years

The first virus capable of infecting DOS-based PCs celebrates its silver jubilee this month.

The Brain Virus, written by Pakistani brothers Basit and Amjad Alvi, was relatively harmless. The Alvis claimed the malware was there as a copyright protection measure to protect their medical software from piracy, an article by CIO magazine on the anniversary recalls.

Brain replaced the boot sector of an infected floppy disk with malicious code, moving the real boot sector to another part of the disc. The malware had the effect of slowing down disk access and, more rarely, making some disks unusable.

Any other floppies used on a machine while the virus was in memory would get infected, but the malware did not copy itself to hard disk drives, as explained in a write-up here.

The Lahore-based Alvi brothers were fairly upfront about their questionable actions, going as far as embedding their names and business address in the malware code. Although intended only to target copyright violators, the malware infected machines in the US and UK among other places.

It's hard to believe now, but the very few computer viruses prior to Brain infected early Apple or Unix machines.

It is highly unlikely any of today's generation of VXers would do the same. Instead of curios such as the Brain virus, security threats these days take the more ominous form of Zombie botnet clients.

The Alvi brothers could never have imagined we'd get here, even though they arguably helped pave a small part of the way towards a world of Windows malware. ®

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