An exploit is a piece of code, a chunk of data, or a sequence of commands that takes advantage of a software vulnerability or security flaw in an application or a system to cause unexpected behaviour to occur. The name comes from the English verb to exploit, which means "to use something to one's advantage". The target of an attack suffers from a design flaw that allows creating the means to access and use it in his interest.
It is written either by security researchers as a proof-of-concept threat or by malicious actors for use in their operations. Exploits allow an intruder to access a network and gain elevated privileges remotely, or move deeper into the network.
The exploit can be used as part of a multi-component attack in some cases. Instead of using a malicious file, the exploit may drop another malware that can include backdoor spyware and Trojans. These backdoors malware are generally used to steal user information from the infected systems.
The most well-known web-based security vulnerabilities are cross-site scripting, cross-site request forgery, SQL injection attacks, and broken authentication code or security misconfigurations. The exploits can be classified into two main categories, such as:
The zero-day vulnerabilities are the most dangerous because they occur when software contains critical security vulnerability of which the vendor is unaware. The vulnerability only becomes known when a hacker is detected exploiting the vulnerability, so it is called a zero-day exploit. Once an exploit occurs, systems running the software are left vulnerable to an attack until the vendor releases a patch to correct the vulnerability, and the patch is applied to the software.
How do Exploits Attack?
Once an exploit has been used, it becomes known to the software developers of the vulnerable system, often fixed through a patch, and becomes unusable.
Because of this reason, many cybercriminals, as well as government agencies or military, do not publish exploits to CVE but choose to keep them private. This vulnerability is known as a zero-day vulnerability or zero-day exploit.
For example, the NSA is a government agency which chooses to keep a software vulnerability private that is EternalBlue.
EternalBlue exploited legacy versions of the Microsoft Windows operating system that used an outdated version of the Server Message Block (SMB) protocol.
Cybercriminals developed the WannaCry ransomware worm that exploited EternalBlue, and it spread to an estimated more than 200,000 computers across 150 countries with damages ranging from 100 million to billions of dollars before EternalBlue was patched.
Despite software developers issuing a patch to fix EternalBlue, this known vulnerability continues to be a large cybersecurity risk because of the poor user adoption of the patch.
Classification of Exploit
There are several methods of classifying exploits. The most common is how the exploit communicates with the vulnerable software.
A remote exploit works over a network and exploits the security vulnerability without any prior access to the vulnerable system.
A local exploit requires prior access to the vulnerable system and increases the privileges of the person running the exploit past those granted by the system administrator. Exploits against client applications also exist, consisting of modified servers that send an exploit if accessed with a client application.
Exploits against client applications may also require some interaction with the user and thus may be used in combination with the social engineering method. Another classification is the action against the vulnerable system such as unauthorized data access, arbitrary code execution, and denial of service.
Many exploits are designed to provide super user-level access to a computer system. It is also possible to use several exploits, first to gain low-level access, and then to escalate privileges repeatedly until one reaches the highest administrative level called root.
After an exploit is made known to the authors of the affected software, the vulnerability is often fixed through a patch, and the exploit becomes unusable. This is the reason why some black hat hackers, as well as military or intelligence agencies hackers, do not publish their exploits and keep them private.
Exploits unknown to everyone but the people that found and developed them are referred to as zero-day exploits.
Types of Exploit
Exploits can be categorized in several different ways, depending on how the exploits work and what type of attacks they can accomplish.
The most familiar type of exploit is the zero-day exploit, which takes advantage of a zero-day vulnerability. The zero-day vulnerability occurs when a piece of software usually an application or an operating system contains a critical security vulnerability of which the vendor is unaware. The vulnerability only becomes known when a hacker is detected exploiting the vulnerability, hence the term zero-day exploit.
Once such an exploit occurs, systems running the software are left vulnerable to an attack until the vendor releases a patch to correct the vulnerability, and the patch is applied to the software.
Security exploits come in all shapes and sizes, but some techniques are used more often than others. Some of the most common web-based security vulnerabilities include SQL injection attacks, cross-site request forgery, and cross-site scripting, as well as abuse of broken authentication code or security misconfigurations.
Exploits can be characterized by the expected result of the attack, such as a denial of service, remote code execution, privilege escalation, malware delivery or other malicious goals. Computer exploits may also be characterized by the type of vulnerability being exploited, including buffer overflow exploits, code injection or other types of input validation vulnerabilities and side-channel attacks.
Virtual patching is one of the most recommended mitigation solutions for enterprises. Virtual patching works on the premise that exploits take a definable path to and from an application to use a software flaw.
It is possible to create rules at the network layer that can control communication with target software.
How can Protect System from Exploits?
Here are a few methods to get proactive about exploit protection, such as: