Departamento de Informática
Cátedra de Inglés - Nivel III

Mgter. Adriana Martín

MeDHiME - Metodología para Desarrollos Hipermediales de Materiales Educativos

Defending your PC against the attack of the killer code Portable Computing July, 1998

Viruses are a major problem for computer users, especially users of microcomputer systems.
Multi-user computers, generally are not prone to viruses because the executable programs are
protected from writing by the operating system. Even if a virus does infect a program, its powers
are limited because other aspects of the system are protected. Single-user systems, do not have
such protections and, as a result, a virus has free run.
Like worms, viruses are designed to spread into other programs and can wreak havoc in
a system, including modifying or destroying files, and causing system crashes and program
malfunctions. Unlike a worm, which is structured as a complete standalone program, a virus is a
fragment of code embedded in a legitimate program.
The way viruses attach themselves to the system determines their classification: “program”
viruses link to executable files, “boot” viruses infect the boot record, and “multipartite” viruses infect
both the programs and boot sections. Common symptoms of infection are: changes in program size,
programs taking longer to load, strange or modified file names, unexpected files that suddenly appear
on your computer, and false file-modification dates.
Viruses usually spread through the Internet: upon downloading viral programs from public
bulletin boards, opening e-mails with or without an attachment, or exchanging floppy disks containing
an infection. Contrary to popular opinion, viruses can not infect a computer immediately upon
downloading an infected program or popping a floppy into a diskette drive. The virus can only be
activated when the infected program is run or the boot record is read.
The first line of defense against viruses is to keep a write-protected backup copy of your
system disks. This procedure won´t stop a virus from infecting the system, but it will make the
restoration process much easier. Actually, the best protection against computer viruses is prevention,
or the practice of safe computing. Purchasing unopened software from vendors and avoiding free or
pirated copies from public sources or floppy-disk exchange is the safest route to preventing infection.
Another safeguard, while not preventing infection, does permit early detection. Antivirus
programs work by searching all the programs on a system for the specific pattern of instructions
that make up the virus. When they find a known pattern, they remove the instructions, thereby
“disinfecting” the program. However, since new viruses are being constantly developed, these
troubleshooting programs are only useful if they are continually updated. There are solid antivirus
programs that scan new acquisitions and watch the system for signs of virus infestation, adding the
new data to the list of clues they scan for.
So don’t double click or run anything until your antivirus program scans it. If it finds a virus,
exit any programs you are running (other than the antivirus program). If it recognizes the virus, it
should be able to easily remove it from your system. But, if the virus is newer than your scanning
program, this one won’t recognize it and you will get a false negative. If you update your antivirus
program regularly and let it scan everything before you run it, you will probably never get a virus.