Friday the 13th occurs three times in 1998, it’s going to be a worrying year for superstitious PC owners. It’s a favourite date for triggering computer viruses but  relax, the chances of your PC catching a nasty infection are actually quite small, provided you take a few simple precautions.

Nevertheless, the risk exists and with the growth of the PC population, the internet and the ingenuity of virus creators, it is increasing all the time. But what exactly is a computer virus, and what are the dangers to your PC?

Broadly speaking a virus is any program that gets into your PC, without your permission, and interferes with its normal operation. At the last count there were more than 15,000 of them. As it happens most are relatively benign and do little actual harm, apart from messing around with the display or putting up irritating messages on the monitor screen. Others though can do real damage, to the data on your PC or the network, by scrambling or concealing files, causing unpredictable behaviour. In extreme cases a virus can trash the hard disc drive in your computer, where all of your programs and files are stored.

Viruses come in all shapes and sizes but they’ve all got individual characteristics or ‘signatures, that can be identified by up-to-date anti-virus scanning software. Some of the hardest to detect lurk in the Master Boot Sector, that’s an area of your hard disc containing important software, that controls how your PC operates. From there viruses can spread to floppy discs and infect other machines. 

Almost as virulent are memory resident or TSR file viruses, which can also take over a PCs operating system and make it do unpleasant things to files and data. They live quietly in the computer’s memory and spread by infecting files containing programs and drivers. They’re the ones that end in the letters .EXE, .COM or .SYS.

Stealth and polymorphic viruses are cunning little devils. They’re a bit like their biological counterparts. They can change their appearance and incorporate themselves into legitimate pieces of software, making detection and eradication that much more difficult. Some hide by making sure that the size of the host program doesn’t change, after it has been infected. Others alter their signature code after each infection, to avoid being identified by scanning software

Macro viruses are comparatively new and a threat tp PCs running word processing and spread sheet programs. They’re written in a programming language that makes the program perform a repetitive task or ‘macro’. The trouble is, macros can be hidden inside text and data files and easily transferred from PC to PC via infected discs and Email. Once the file is opened the virus goes about its business, changing and corrupting other files.

Incidentally, your PC cannot become infected by plain text Emails. Viruses are be hidden inside attachments and programs, and they only become active when they’re opened or executed. It’s fair to say that the Internet is generally safe, though it’s sensible to avoid downloading material from obscure or suspicious-looking sites.  

If your PCs is mostly used for game playing or word-processing then you haven’t much to worry about. The odds start to rise when your machine is connected to the internet or a network, you swap discs with other PC owners or you buy bootleg and pirate software. The odd virus has also popped up on free magazine cover mounted CD ROMs. If your PC falls into any of those categories, you have already experienced an infection or your machine is behaving erratically, then it’s time to get hold of some anti-virus software.

Most anti-virus programs carry out a preliminary scan as they’re loading, so you start with a clean slate. After that they check vulnerable areas of your disc drive and memory, every time the PC is switched on. All new software coming onto the machine is checked, whether it’s on disc, CD-ROM or downloaded from the internet.

Anti-virus software is only as good as its signature library. Most programs can be updated, with signatures of the newest viruses, either automatically from the manufacturer’s internet web site, or on floppy disc.

If an infection is detected scanning software immediately puts up a warning message on the screen, and stops any further potentially damaging disc writing activities. The affected files are then isolated or ‘quarantined’, so they can be safely disinfected, deleted or renamed, if the software regards them as harmless.

Don’t get paranoid but do take precautions. There’s only three weeks to go before February Friday the 13th!


Cheyenne Anti Virus £48

Roderick Manhatten Group Ltd., 0181-875 4441


Dr Solomons Anti Virus Toolkit, Win 95, £80

Dr Solomon UK, telephone (01296) 318700 


McAfee VirusScan V3,  £50

McAfee, telephone (01344) 304730


Norton AntiVirus Deluxe 4.0, £50

Symantec UK, telephone 0171-616 5600


PC-cillin 95, £34

Roderick Manhatten Group Ltd., 0181-875 4441


Sophos Anti-Virus 3.0, £120

Sophos plc, telephone (01235) 559933



Extensions -- files ending in .EXE or .COM usually contain executable programs; .SYS files are mostly used for driver software, used by the PC to communicate with hardware devices

SoHo -- small office/home office

TSR -- terminate and stay resident, programs that load automatically into the computer’s memory and operate in the background until needed


From the Start menu in Windows 95 click on Settings, Control Panel, and then on the Mouse icon. There you will find a range of settings, that control the way your mouse behaves. There’s also the opportunity to change the button configuration, useful if you are left-handed. The two most important parameters for PC newcomers are Motion and Click Speed; set both to slow and you’ll find the mouse much easier to control. Increase the speed once you get used to how the mouse reacts. Whilst you’re there click on the Pointers tab and the Scheme menu, then select the Animated Hourglasses option. This will make waiting for things to happen just a little more interesting...

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