Bots as malware
Each Internet user knows the concept of bot (Internet-bot, robot, www-bot etc.). This program was specially created to perform tasks automatically through the interfaces utilized by the user.
Bots are designed to perform monotonous and often repeating work with high speed and on conditions that require quick reaction. Gaming bots, auction-site bots and chat bots are widespread in this respect.
For each bot on the server they place a file, which limits its activity.
In general, bots can be quite useful:
- They are used for access to media
- Bots often control hosts
- Bots deliver data
- Bots can give appropriate answer to the question. These bots are often used in chats as well as for announcing some results (weather, matches, exchange rate etc.)
The most spread types of bots: computer game bot (simulating the player actions), search engine spider (automated site scanning), answering machine (chat, email).
Malicious purposes
Despite of their relative advantages, bots can often be used to harm the operating system. This can be either computer attack or Internet fraud.
The principal malicious activity of such software is:
1. Spambots: harvest all addresses from guestbook pages or contact forms;
2. Bots that overload the channel with big flow of advertising info(generally, it's of commercial nature);
3. Bots that harvest information on innocuous sites and then use it in automatic doorways (type of spam, a page optimized for search query. The aim is first positions in the search results on this query);
4. Bots can be a virus or a worm;
5. Botnets (computer networks ran by bots). A bot included in the botnet is secretly installed program that is set up on the victim's computer and let the hacker use the resources of this computer. Botnets are mainly used to spread spam and disclosure passwords.
6. Zombie-computers (computers in the network that are used by strangers without awareness of their owners). The process of turning such computers into "zombies" is usually performed with the help of Trojan, which set there a task necessary to the hacker. Zombie-computers are used to get access to the closed network, for clustering, spreading spam, DDoS attacks etc. By the way, "zombies" are very efficient tools of spreading spam: they are responsible for sending 50-80% of spam all over the world.
How to fight with them?
At this moment the most widespread method of fighting automated activity of bots is CAPTCHA.
CAPTCHA is a completely automated Turing test, developed to discern computers from people. In order to confirm the fact that it is a person who is working with the system at the moment, a user is offered to identify graphic text, which can relatively easy read by a person, but is difficult for robots.