Viruses and more :: Viruses and other malware


Adware is software that presents banner ads or in pop-up windows through a bar that appears on a computer screen. These advertisements usually cannot be removed and are consequently always visible. The connection data allow many conclusions on the usage behavior and are problematic in terms of data security.


A backdoor can gain access to a computer by going around the computer access security mechanisms.

A program that is being executed in the background generally enables the attacker almost unlimited rights. User's personal data can be spied with the backdoor's help, but are mainly used to install further computer viruses or worms on the relevant system. The connection data allow many conclusions on the usage behavior and are problematic in terms of data security.

Boot viruses

The boot or master boot sector of hard disks is mainly infected by boot sector viruses. They overwrite important information necessary for the system execution. One of the awkward consequences: the computer system cannot be loaded any more&ldots;


A bot net is defined as a remote network of PCs (on the Internet), which is composed of bots that communicate with each other. A Bot-Net can comprise a collection of cracked machines running programs (usually referred to as worms, Trojans) under a common command and control infrastructure. Bot-Nets serve various purposes, including Denial-of-service attacks etc., partly without the affected PC user's knowledge. The main potential of Bot-Nets is that the networks can achieve dimensions on thousands of computers and its bandwidth sum bursts most conventional Internet accesses.


An exploit (security gap) is a computer program or script that takes advantage of a bug, glitch or vulnerability leading to privilege escalation or denial of service on a computer system. A form of an exploit for example are attacks from the Internet with the help of manipulated data packages. Programs can be infiltrated in order to obtain higher access.

Hoaxes hoax - Scherz, Schabernack, Ulk)

For several years, internet and other network users have received alerts about viruses that are purportedly spread via email. These alerts are spread per email with the request that they should be sent to the highest possible number of colleagues and to other users, in order to warn everyone against the "danger".


A honeypot is a service (program or server) installed in a network. It has the function to monitor a network and to protocol attacks. This service is unknown to the legitimate user - because of this reason he is never addressed. If an attacker examines a network for the weak points and uses the services which are offered by a Honeypot, it is logged and an alert is triggered.

Macro viruses

Macro viruses are small programs that are written in the macro language of an application (e.g. WordBasic under WinWord 6.0) and that can normally only spread within documents of this application. Because of this, they are also called document viruses. In order to be active, they need that the corresponding applications are activated and that one of the infected macros has been executed. Unlike "normal" viruses, macro viruses do consequently not attack executable files but they do attack the documents of the corresponding host-application.


Pharming is a manipulation of the host file of web browsers to divert enquiries to spoofed websites. This is a further development of classic phishing. Pharming fraudsters operate their own large server farms on which fake websites are stored. Pharming has established itself as an umbrella term for various types of DNS attacks. In the case of a manipulation of the host file, a specific manipulation of a system is carried out with the aid of a Trojan or virus. The result is that the system can now only access fake websites, even if the correct web address is entered.


Phishing means angling for personal details of the Internet user. Phishers generally send their victims apparently official letters such as emails that are intended to induce them to reveal confidential information to the culprits in good faith, in particular user names and passwords or PINs and TANs of online banking accounts. With the stolen access details, the phishers can assume the identities of the victims and carry out transactions in their name. What is clear is that banks and insurance companies never ask for credit card numbers, PINs, TANs or other access details by email, SMS or telephone.

Polymorph viruses

Polymorph viruses are the real masters of disguise. They change their own programming codes - and are therefore very hard to detect.

Program viruses

A computer virus is a program that is capable to attach itself to other programs after being executed and cause an infection. Viruses multiply themselves unlike logic bombs and Trojans. In contrast to a worm, a virus always requires a program as host, where the virus deposits his virulent code. The program execution of the host itself is not changed as a rule.


A rootkit is a collection of software tools that are installed after a computer system has been infiltrated to conceal logins of the infiltrator, hide processes and record data - generally speaking: to make themselves invisible. They attempt to update already installed spy programs and reinstall deleted spyware.

Script viruses and worms

Such viruses are extremely easy to program and they can spread - if the required technology is on hand - within a few hours via email round the globe.

Script viruses and worms use one of the script languages, such as Javascript, VBScript etc., to insert themselves in other, new scripts or to spread themselves by calling operating system functions. This frequently happens via email or through the exchange of files (documents).

A worm is a program that multiplies itself but that does not infect the host. Worms can consequently not form part of other program sequences. Worms are often the only possibility to infiltrate any kind of damaging programs on systems with restrictive security measures.


Spyware are so called spy programs that intercept or take partial control of a computer's operation without the user's informed consent. Spyware is designed to exploit infected computers for commercial gain.

Trojan horses (short Trojans)

Trojans are pretty common nowadays. We are talking about programs that pretend to have a particular function, but that show their real image after execution and carry out a different function that, in most cases, is destructive. Trojan horses cannot multiply themselves, which differentiates them from viruses and worms. Most of them have an interesting name (SEX.EXE or STARTME.EXE) with the intention to induce the user to start the Trojan. Immediately after execution they become active and can, for example, format the hard disk. A dropper is a special form of Trojan that 'drops' viruses, i.e. embeds viruses on the computer system.


A Zombie-PC is a computer that is infected with malware programs and that enables hackers to abuse computers via remote control for criminal purposes. On command, the affected PC starts denial-of-service (DoS) attacks, for example, or sends spam and phishing emails.