Computer security
![]() Computer security (also cybersecurity, digital security, or information technology (IT) security) is a subdiscipline within the field of information security. It focuses on protecting computer software, systems, and networks from threats that can lead to unauthorized information disclosure, theft or damage to hardware, software, or data, as well as from the disruption or misdirection of the services they provide.[1][2] The growing significance of computer insecurity reflects the increasing dependence on computer systems, the Internet,[3] and evolving wireless network standards. This reliance has expanded with the proliferation of smart devices, including smartphones, televisions, and other components of the Internet of things (IoT). As digital infrastructure becomes more embedded in everyday life, cybersecurity has emerged as a critical concern. The complexity of modern information systems—and the societal functions they underpin—has introduced new vulnerabilities. Systems that manage essential services, such as power grids, electoral processes, and finance, are particularly sensitive to security breaches.[4][5]
Vulnerabilities and attacksA vulnerability refers to a flaw in the structure, execution, functioning, or internal oversight of a computer or system that compromises its security. Most of the vulnerabilities that have been discovered are documented in the Common Vulnerabilities and Exposures (CVE) database.[6] An exploitable vulnerability is one for which at least one working attack or exploit exists.[7] Actors maliciously seeking vulnerabilities are known as threats. Vulnerabilities can be researched, reverse-engineered, hunted, or exploited using automated tools or customized scripts.[8][9] Various people or parties are vulnerable to cyber attacks; however, different groups are likely to experience different types of attacks more than others.[10] In April 2023, the United Kingdom Department for Science, Innovation & Technology released a report on cyber attacks over the previous 12 months.[11] They surveyed 2,263 UK businesses, 1,174 UK registered charities, and 554 education institutions. The research found that "32% of businesses and 24% of charities overall recall any breaches or attacks from the last 12 months." These figures were much higher for "medium businesses (59%), large businesses (69%), and high-income charities with £500,000 or more in annual income (56%)."[11] Yet, although medium or large businesses are more often the victims, since larger companies have generally improved their security over the last decade, small and midsize businesses (SMBs) have also become increasingly vulnerable as they often "do not have advanced tools to defend the business."[10] SMBs are most likely to be affected by malware, ransomware, phishing, man-in-the-middle attacks, and Denial-of Service (DoS) Attacks.[10] Normal internet users are most likely to be affected by untargeted cyberattacks.[12] These are where attackers indiscriminately target as many devices, services, or users as possible. They do this using techniques that take advantage of the openness of the Internet. These strategies mostly include phishing, ransomware, water holing and scanning.[12] To secure a computer system, it is important to understand the attacks that can be made against it, and these threats can typically be classified into one of the following categories: BackdoorA backdoor in a computer system, a cryptosystem, or an algorithm is any secret method of bypassing normal authentication or security controls. These weaknesses may exist for many reasons, including original design or poor configuration.[13] Due to the nature of backdoors, they are of greater concern to companies and databases as opposed to individuals. Backdoors may be added by an authorized party to allow some legitimate access or by an attacker for malicious reasons. Criminals often use malware to install backdoors, giving them remote administrative access to a system.[14] Once they have access, cybercriminals can "modify files, steal personal information, install unwanted software, and even take control of the entire computer."[14] Backdoors can be difficult to detect, as they often remain hidden within the source code or system firmware intimate knowledge of the operating system of the computer. Denial-of-service attackDenial-of-service attacks (DoS) are designed to make a machine or network resource unavailable to its intended users.[15] Attackers can deny service to individual victims, such as by deliberately entering a wrong password enough consecutive times to cause the victim's account to be locked, or they may overload the capabilities of a machine or network and block all users at once. While a network attack from a single IP address can be blocked by adding a new firewall rule, many forms of distributed denial-of-service (DDoS) attacks are possible, where the attack comes from a large number of points. In this case, defending against these attacks is much more difficult. Such attacks can originate from the zombie computers of a botnet or from a range of other possible techniques, including distributed reflective denial-of-service (DRDoS), where innocent systems are fooled into sending traffic to the victim.[15] With such attacks, the amplification factor makes the attack easier for the attacker because they have to use little bandwidth themselves. To understand why attackers may carry out these attacks, see the 'attacker motivation' section. Physical access attacksA direct-access attack is when an unauthorized user (an attacker) gains physical access to a computer, most likely to directly copy data from it or steal information.[16] Attackers may also compromise security by making operating system modifications, installing software worms, keyloggers, covert listening devices or using wireless microphones. Even when the system is protected by standard security measures, these may be bypassed by booting another operating system or tool from a CD-ROM or other bootable media. Disk encryption and the Trusted Platform Module standard are designed to prevent these attacks. Direct service attackers are related in concept to direct memory attacks which allow an attacker to gain direct access to a computer's memory.[17] The attacks "take advantage of a feature of modern computers that allows certain devices, such as external hard drives, graphics cards, or network cards, to access the computer's memory directly."[17] EavesdroppingEavesdropping is the act of surreptitiously listening to a private computer conversation (communication), usually between hosts on a network. It typically occurs when a user connects to a network where traffic is not secured or encrypted and sends sensitive business data to a colleague, which, when listened to by an attacker, could be exploited.[18] Data transmitted across an open network allows an attacker to exploit a vulnerability and intercept it via various methods. Unlike malware, direct-access attacks, or other forms of cyber attacks, eavesdropping attacks are unlikely to negatively affect the performance of networks or devices, making them difficult to notice.[18] In fact, "the attacker does not need to have any ongoing connection to the software at all. The attacker can insert the software onto a compromised device, perhaps by direct insertion or perhaps by a virus or other malware, and then come back some time later to retrieve any data that is found or trigger the software to send the data at some determined time."[19] Using a virtual private network (VPN), which encrypts data between two points, is one of the most common forms of protection against eavesdropping. Using the best form of encryption possible for wireless networks is best practice, as well as using HTTPS instead of an unencrypted HTTP.[20] Programs such as Carnivore and NarusInSight have been used by the Federal Bureau of Investigation (FBI) and NSA to eavesdrop on the systems of internet service providers. Even machines that operate as a closed system (i.e., with no contact with the outside world) can be eavesdropped upon by monitoring the faint electromagnetic transmissions generated by the hardware. TEMPEST is a specification by the NSA referring to these attacks. MalwareMalicious software (malware) is any software code or computer program "intentionally written to harm a computer system or its users."[21] Once present on a computer, it can leak sensitive details such as personal information, business information and passwords, can give control of the system to the attacker, and can corrupt or delete data permanently.[22][23] Types of malware
Man-in-the-middle attacksMan-in-the-middle attacks (MITM) involve a malicious attacker trying to intercept, surveil or modify communications between two parties by spoofing one or both party's identities and injecting themselves in-between.[24] Types of MITM attacks include:
Multi-vector, polymorphic attacksSurfacing in 2017, a new class of multi-vector,[25] polymorphic[26] cyber threats combine several types of attacks and change form to avoid cybersecurity controls as they spread. Multi-vector polymorphic attacks, as the name describes, are both multi-vectored and polymorphic.[27] Firstly, they are a singular attack that involves multiple methods of attack. In this sense, they are "multi-vectored" (i.e. the attack can use multiple means of propagation such as via the Web, email and applications). However, they are also multi-staged, meaning that "they can infiltrate networks and move laterally inside the network."[27] The attacks can be polymorphic, meaning that the cyberattacks used such as viruses, worms or trojans "constantly change ("morph") making it nearly impossible to detect them using signature-based defences."[27] Phishing![]() Phishing is the attempt of acquiring sensitive information such as usernames, passwords, and credit card details directly from users by deceiving the users.[28] Phishing is typically carried out by email spoofing, instant messaging, text message, or on a phone call. They often direct users to enter details at a fake website whose look and feel are almost identical to the legitimate one.[29] The fake website often asks for personal information, such as login details and passwords. This information can then be used to gain access to the individual's real account on the real website. Preying on a victim's trust, phishing can be classified as a form of social engineering. Attackers can use creative ways to gain access to real accounts. A common scam is for attackers to send fake electronic invoices[30] to individuals showing that they recently purchased music, apps, or others, and instructing them to click on a link if the purchases were not authorized. A more strategic type of phishing is spear-phishing which leverages personal or organization-specific details to make the attacker appear like a trusted source. Spear-phishing attacks target specific individuals, rather than the broad net cast by phishing attempts.[31] Privilege escalationPrivilege escalation describes a situation where an attacker with some level of restricted access is able to, without authorization, elevate their privileges or access level.[32] For example, a standard computer user may be able to exploit a vulnerability in the system to gain access to restricted data; or even become root and have full unrestricted access to a system. The severity of attacks can range from attacks simply sending an unsolicited email to a ransomware attack on large amounts of data. Privilege escalation usually starts with social engineering techniques, often phishing.[32] Privilege escalation can be separated into two strategies, horizontal and vertical privilege escalation:
Side-channel attackAny computational system affects its environment in some form. This effect it has on its environment can range from electromagnetic radiation, to residual effect on RAM cells which as a consequence make a Cold boot attack possible, to hardware implementation faults that allow for access or guessing of other values that normally should be inaccessible. In Side-channel attack scenarios, the attacker would gather such information about a system or network to guess its internal state and as a result access the information which is assumed by the victim to be secure. The target information in a side channel can be challenging to detect due to its low amplitude when combined with other signals [33] Social engineeringSocial engineering, in the context of computer security, aims to convince a user to disclose secrets such as passwords, card numbers, etc. or grant physical access by, for example, impersonating a senior executive, bank, a contractor, or a customer.[34] This generally involves exploiting people's trust, and relying on their cognitive biases. A common scam involves emails sent to accounting and finance department personnel, impersonating their CEO and urgently requesting some action. One of the main techniques of social engineering are phishing attacks. In early 2016, the FBI reported that such business email compromise (BEC) scams had cost US businesses more than $2 billion in about two years.[35] In May 2016, the Milwaukee Bucks NBA team was the victim of this type of cyber scam with a perpetrator impersonating the team's president Peter Feigin, resulting in the handover of all the team's employees' 2015 W-2 tax forms.[36] SpoofingSpoofing is an act of pretending to be a valid entity through the falsification of data (such as an IP address or username), in order to gain access to information or resources that one is otherwise unauthorized to obtain. Spoofing is closely related to phishing.[37][38] There are several types of spoofing, including:
In 2018, the cybersecurity firm Trellix published research on the life-threatening risk of spoofing in the healthcare industry.[40] TamperingTampering describes a malicious modification or alteration of data. It is an intentional but unauthorized act resulting in the modification of a system, components of systems, its intended behavior, or data. So-called Evil Maid attacks and security services planting of surveillance capability into routers are examples.[41] HTML smugglingHTML smuggling allows an attacker to smuggle a malicious code inside a particular HTML or web page.[42] HTML files can carry payloads concealed as benign, inert data in order to defeat content filters. These payloads can be reconstructed on the other side of the filter.[43] When a target user opens the HTML, the malicious code is activated; the web browser then decodes the script, which then unleashes the malware onto the target's device.[42] Information security practicesEmployee behavior can have a big impact on information security in organizations. Cultural concepts can help different segments of the organization work effectively or work against effectiveness toward information security within an organization. Information security culture is the "...totality of patterns of behavior in an organization that contributes to the protection of information of all kinds."[44] Andersson and Reimers (2014) found that employees often do not see themselves as part of their organization's information security effort and often take actions that impede organizational changes.[45] Indeed, the Verizon Data Breach Investigations Report 2020, which examined 3,950 security breaches, discovered 30% of cybersecurity incidents involved internal actors within a company.[46] Research shows information security culture needs to be improved continuously. In "Information Security Culture from Analysis to Change", authors commented, "It's a never-ending process, a cycle of evaluation and change or maintenance." To manage the information security culture, five steps should be taken: pre-evaluation, strategic planning, operative planning, implementation, and post-evaluation.[47]
Computer protection (countermeasures)In computer security, a countermeasure is an action, device, procedure or technique that reduces a threat, a vulnerability, or an attack by eliminating or preventing it, by minimizing the harm it can cause, or by discovering and reporting it so that corrective action can be taken.[48][49][50] Some common countermeasures are listed in the following sections: Security by designSecurity by design, or alternately secure by design, means that the software has been designed from the ground up to be secure. In this case, security is considered a main feature. The UK government's National Cyber Security Centre separates secure cyber design principles into five sections:[51]
These design principles of security by design can include some of the following techniques:
Security architectureSecurity architecture can be defined as the "practice of designing computer systems to achieve security goals."[52] These goals have overlap with the principles of "security by design" explored above, including to "make initial compromise of the system difficult," and to "limit the impact of any compromise."[52] In practice, the role of a security architect would be to ensure the structure of a system reinforces the security of the system, and that new changes are safe and meet the security requirements of the organization.[53][54] Similarly, Techopedia defines security architecture as "a unified security design that addresses the necessities and potential risks involved in a certain scenario or environment. It also specifies when and where to apply security controls. The design process is generally reproducible." The key attributes of security architecture are:[55]
Practicing security architecture provides the right foundation to systematically address business, IT and security concerns in an organization. Security measuresA state of computer security is the conceptual ideal, attained by the use of three processes: threat prevention, detection, and response. These processes are based on various policies and system components, which include the following:
Today, computer security consists mainly of preventive measures, like firewalls or an exit procedure. A firewall can be defined as a way of filtering network data between a host or a network and another network, such as the Internet. They can be implemented as software running on the machine, hooking into the network stack (or, in the case of most UNIX-based operating systems such as Linux, built into the operating system kernel) to provide real-time filtering and blocking.[56] Another implementation is a so-called physical firewall, which consists of a separate machine filtering network traffic. Firewalls are common amongst machines that are permanently connected to the Internet. Some organizations are turning to big data platforms, such as Apache Hadoop, to extend data accessibility and machine learning to detect advanced persistent threats.[58] In order to ensure adequate security, the confidentiality, integrity and availability of a network, better known as the CIA triad, must be protected and is considered the foundation to information security.[59] To achieve those objectives, administrative, physical and technical security measures should be employed. The amount of security afforded to an asset can only be determined when its value is known.[60] Vulnerability managementVulnerability management is the cycle of identifying, fixing or mitigating vulnerabilities,[61] especially in software and firmware. Vulnerability management is integral to computer security and network security. Vulnerabilities can be discovered |