The techniques used to facilitate the types of cybercrime that affect the confidentiality, integrity and availability of data and systems are very diverse and more and more sophisticated. Some of the most widespread techniques include:
Malicious software: This includes viruses, spyware, and other unwanted software that is installed on computers and other devices without permission and performs unwanted tasks, often for the benefit of the attacker. These programs can damage devices, and can be used to steal personal information, monitor and control online activity, send spam and commit fraud, as well as infect other machines on the network. They also can make devices vulnerable to viruses and deliver unwanted or inappropriate online advertisements.
Viruses, trojan horses, adware, and spyware are all types of malware. A virus can replicate itself and spread to other devices, without the user being aware. Although some viruses are latent, most of them are intended to interfere with data or affect the performance of devices (reformatting the hard disk, using up computer memory, etc). A trojan horse is a type of malware that is often disguised as legitimate software. Trojans can be employed by cyber-thieves and hackers trying to gain access to users' systems. Users are typically tricked by some form of social engineering into loading and executing Trojans on their systems. Once activated, Trojans can enable cyber-criminals to spy on users, steal sensitive data, and gain backdoor access to users’ system. Adware collects marketing data and other information without the user's knowledge, or redirects search requests to certain advertising websites. Spyware monitors users, gathers information about them and transmits it to interested parties, without the users being aware. Types of information gathered can include: the websites visited, browser and system information, the computer IP address, as well as more sensitive information such as e-mail addresses, and passwords. Additionally, malware can cause browser hijacking, in which the user’s browser settings are modified without permission. The software may create desktop shortcuts, display advertising pop-ups, as well as replace existing home pages or search pages with other pages.
Botnets: Botnets are networks of hijacked personal computers that perform remotely commanded tasks without the knowledge of their owners. A computer is turned into a bot after being infected with specific type of malware which allows remote control. Botnets are used for a wide variety of crimes and attacks: distributing spam, extending malware infections to more computers, contributing to pay-per-click fraud, or identity theft. One of the most worrying uses of botnets is to perform distributed denial of service (DDoS) attacks.
Researchers and cybersecurity companies have warned that botnets are becoming the biggest Internet security threat, as they are increasing the effects of viruses and other malicious programs, raising information theft, and boosting denial of service attacks. As an illustration of the dimension of this threat, the Simda botnet, taken down in April 2015, affected computers in 190 countries and involved the use of 14 command-and-control servers in five countries.
Denial of service (DoS) attacks: These attacks involve flooding a computer or website with information, preventing them to function properly. These attacks are aimed to exhaust the resources available to a network, application or service, in order to prevent users from accessing them. They are more frequently aimed at businesses, rather than individuals. Distributed denial-of-service (DDoS) attacks are those attacks in which multiple compromised computers attack a single target.
A DoS attack does not usually result in the theft of information or other security loss, but it can cause financial or time loss to the affected organisation or individual, because of its effects (particular network services becoming unavailable, websites ceasing operation, targeted email accounts prevented from receiving legitimate emails, etc.)