Botnets are a growing threat to Internet security and can be defined as a set of compromised devices connected to a network that are used to perform various attacks controlled by one or more attackers. Botnet creation is done by placing malicious code in a device using a social engineering technique or by exploitation a system vulnerability, which then connects to a central server or other device while waiting for orders from the main attacker. There are 3 botnet structures, a centralized one that uses one or more C&C servers, a P2P structure in which bots have the role of both a client and a server, and a hybrid one that is a combination of the two previous ones. Botnet detection can be divided into passive techniques where the informations are drawn by only observing the network, as well as active techniques in which certain actions are applied. By applying right conutermeasures, combining technical and social aspects can lead to the desired results, which includes reducing the dominance of botnets.