Six computer viruses and how to protect yourself from them

If computer viruses were harmful to human health, the world’s population would have pretty much drastically reduced within the last 30 years. Computer viruses are still the worst case scenario for the average PC user 32 years after they were "invented" by US American Fred Cohen, and claim billions of "victims" every year. The term "viruses" is familiar to most users; however, what exactly this term, which is actually rooted in biology, describes is foreign to the majority. Learn what types of viruses there are and how to protect yourself from them here.


PC viruses – (unfortunately) a recipe for success

In 1983, Fred Cohen, now a renowned researcher and professor in the field of IT security, created a program as part of his doctoral thesis that could infect, modify and subsequently spread through other applications. The computer virus was born. Its triumphant march continues to this day because its original properties have basically not changed and PC viruses, much like their biological counterparts, are constantly changing their facade, making it nearly impossible to develop a "cure".

In total, there are six broad supercategories of viruses, whose transitions are fluid and whose characteristics often occur in combination. The exact characterization of a virus is therefore hardly possible.

The boot sector virus prevents the computer from booting up

The oldest virus is the so-called boot sector virus. It got its name because it nests on the boot sector – the part of the hard drive where the program to start the PC is located – and alters it so that the PC will not boot up. The boot sector virus was very common, especially in the 1980s and 1990s, and was mostly transmitted through floppy disks, which were the common removable media at the time.

Trojans – their camouflage misleads the user

Boot sector viruses are certainly far less familiar to today’s PC user generation than Trojans, which camouflage themselves outwardly as seemingly harmless programs. They allow unauthorized persons to access a computer via the Internet, where they can then often cause great damage and spy out personal data. Often Trojans are sent by hackers in the form of spam. Last year, spam mails circulated disguised as a Telekom invoice, with the Trojan hiding in the supposed invoice attachment. If the recipient of the mail opened the attachment, the virus could automatically implant itself.

Script viruses, the danger in Internet browsers

Script viruses, as the name suggests, infect scripts that run z.B. are built into many Internet pages. They are written in a common programming language such as Javascript or Virtual Basic Script (VBS) and are thus understood by Internet browsers. The browsers execute the virus scripts, infecting the PC. The capabilities of PUA viruses range from automatic emailing to automatic deletion and file name manipulation.

Program virus: be careful when downloading from the Internet!

While script viruses find their host on the Internet, program viruses need programs in order to exert their damaging effect. Similar to Trojans, they are activated when infected programs or files are run. The danger of becoming infected with program viruses is particularly great when downloading unknown files or programs from the Internet.

Macro viruses hide in files and become active when they are opened

Macro viruses also need a host in order to be able to settle in PCs. They are hidden exclusively in Word or Excel files and are launched automatically when opened. Here, too, the spread can take place via e-mails or downloads from the Internet.

Special form: Computer worms can spread on their own

The peculiarity of worms is that they can spread on their own without the help of users. Thus, unlike the other categories, they do not require a host. This classically works in the form of e-mails, which are automatically sent on and on and infect the mailboxes of every recipient. Probably the best-known worm is the computer worm "Loveletter", which spread explosively around the world by e-mail in 2000 and caused an estimated damage of 10 billion dollars. The worm, whose subject was "I love you", primarily destroyed image files and also spied out passwords.

The current state of health of the PC world

The types of viruses described above are still circulating on the world’s computers and are spreading rapidly, a situation that is further facilitated by increasing digitalization. According to the Bitkom digital association, around 8.8 million people in Germany have already had a virus on their computer that has caused damage.

Philipp Wolf, Executive Vice President of Avira Protection Labs on the current threat situation:

Currently we see more and more Adware or so called Potentially Unwanted Applications (PUA). These applications usually piggyback onto computers via installation programs and then display more advertisements, install dubious browser extensions or change the default search engine in order to generate their own sales in this way.

In the case of classic Trojans, in recent weeks we have seen larger waves of emails containing the so-called "Yarwi Trojan", which arrives in the mailbox disguised as an alleged invoice or reminder and is executed by gullible users due to the email’s appearance. In addition to downloading further malware from the Internet, the Trojan can also spy on accounts and access data, for example from online banking.

The customer protects himself best with an up-to-date antivirus program, such as Avira, as well as by regularly updating 3rd party software, such as Java, and regularly installing Windows updates.

In general, we advise all users to be skeptical and cautious with e-mail attachments, even if they come from supposedly known senders. When installing programs you should pay attention to the small print (EULA), and also whether other program or browser extensions are installed. Normally there is always the possibility to check them off.

An insight into further, current events is also always provided by the Avira blog at

Viruses today are difficult to detect at first glance – what to look out for

Older viruses were often characterized by the fact that the infected PC was no longer able to elicit a single response. In some cases, the PCs could not even be booted up at all. The approach of the viruses has changed analogously to the development of the fight strategies in the fact that they act increasingly hidden. That’s why you have to sensitize yourself for indications which can be a hint for a virus infection. Indications are z.B. Restrictions in the access of the operating system on certain drives or data media or a very slowly starting computer. A changed browser page or difficulties in modifying or saving files can also be signs of an infection. Despite all sensitization, the credo "better safe than sorry" should always apply. Every PC should be equipped with an up-to-date antivirus program, as this can fend off most attacks in a relatively simple way.

The best protection – a good antivirus program

With all sensitization, the credo "better safe than sorry" should always apply. Each PC should be equipped absolutely with an up-to-date anti-virus program, since this can recognize and then repel most attacks in relatively simple way at first. The independent virus laboratory AV-Comparatives last determined in 2010 which common antivirus programs react to the "Potentially Unwanted Actions" (PUA), which according to Avira expert Philipp Wolf currently pose the greatest threat to the computer world.

Do you need or have questions about virus protection and want to be sure that your PC is well equipped against viruses?? Then just give us a call. Our support will be happy to advise you!

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