Understanding Exploits

An exploit is a technique, code, or a set of commands that an attacker uses to take advantage of a vulnerability in a system, application, or network. Exploits are one of the most prevalent techniques attackers use to gain unauthorized access, exfiltrate data, disrupt operations, or escalate privileges within a target environment. According to Verizon’s 2024 Data Breach Investigation Report, 2024 saw a 180% increase in the use of exploits in the early stages of successful breaches.

Exploits vary in form and impact; some are simple commands that reveal minor data leaks, while others might involve complex, custom tailored software that fully compromises a system. Understanding exploits and their potential impact is essential for defending against modern cyberattacks and prioritizing responses.

The overall impact and accessibility of exploits can vary greatly depending on the nature of the underlying vulnerability being exploited. Let’s review the most common exploit categories and the impact of some real-world examples.

1. Initial Access Exploits

Initial Access exploits allow attackers to gain unauthorized remote access to a system without needing credentials. Often referred to as Remote Code Execution (RCE) exploits, these enable attackers to execute arbitrary code on a target system, leading to full system compromise. Because they provide an initial foothold, Initial Access exploits are among the most critical types for organizations to defend against, as they open the door for attackers to deploy malware, establish backdoors, and move laterally across a network. The risk is heightened by the fact that these exploits often allow attackers to operate without direct user interaction, making detection and defense particularly challenging.

• Example: Microsoft Exchange ProxyLogon (CVE-2021-26855): Disclosed in March 2021, this vulnerability became a major entry point for Chinese-affiliated advanced persistent threat (APT) group Hafnium and other APT actors. ProxyLogon allowed remote attackers to gain full control over Microsoft Exchange servers without authentication, and it was commonly used to implant web shells for persistent access. The attacks targeted multiple sectors around the globe, including government, healthcare, education, and the private sector. Within weeks of the vulnerability’s disclosure, reports estimated that 10s of thousands of organizations were compromised, incurring substantial costs for detection, containment, and remediation.

2. Remote with Credentials Exploits

Remote with Credentials exploits are a category of exploit where unauthorized remote access to a target system is possible, but requires valid user credentials. Attackers who acquire login credentials through techniques like phishing or credential stuffing can leverage these exploits to access network-bound applications or systems. These exploits can allow an adversary to achieve extensive control over a system or application, but the requirement for credentials complicates the exploitation process, somewhat mitigating the associated risk.

• Example: Cisco's IOS XE Web UI vulnerability (CVE-2023-20273): This vulnerability in the Cisco IOS embedded management system allows a remote, authenticated attacker to execute commands with root privileges on affected devices. In September 2023 Cisco reported that threat actors exploited this vulnerability to escalate privileges and to deploy the "BadCandy" implant, a backdoor web shell that provided attackers with deep and persistent access to compromised networks even after the vulnerability was patched.

3. Local Exploits

Local exploits require attackers to have direct access to the target system and typically involve privilege escalation vulnerabilities. These exploits are often used to elevate privileges once an attacker has already gained a foothold in the system, enabling them to access restricted areas or sensitive data. Local exploits play a critical role in multi-stage attacks, where attackers first gain limited access, perhaps through phishing or other social engineering, and then use local exploits to deepen their control. Although they require some level of access to begin with, local exploits can significantly escalate an attack’s damage potential by broadening attacker privileges.

• Example: Linux Kernel Dirty Pipe vulnerability (CVE-2022-0847): This vulnerability allowed attackers with basic user privileges on a Linux system to escalate their access, effectively enabling them to write to read-only files and gain root-level privileges. The Dirty Pipe vulnerability quickly drew attention as it affected a wide range of Linux distributions and devices, including those widely used in enterprise environments. Threat actors targeted cloud environments and shared systems where local privilege escalation could provide critical advantages, allowing them to access sensitive data or disrupt services.

4. Client-Side Exploits

Client-side exploits target end-user applications, such as web browsers, email clients, or common office productivity software. These exploits are often triggered when a user interacts with malicious content, such as by opening a document or clicking a link. Client-side exploits are particularly effective in targeted attacks, where attackers can deliver malicious payloads to users of vulnerable applications. The damage from these exploits can vary based on the application’s security settings and the level of user privileges. They often serve as an initial foothold, enabling attackers to breach enterprise environments or gain access to sensitive data.

• Example: Follina (CVE-2022-30190): This vulnerability in Microsoft’s Support Diagnostic Tool (MSDT) allowed attackers to execute arbitrary code by tricking users into opening specially-crafted Microsoft Word documents. Exploited by various threat actors, including APT groups, Follina was employed in phishing campaigns aimed at sectors such as government, finance, and healthcare, where it was used to deliver malware and establish footholds in networks with high-value targets.

5. Infoleak Exploits

Information leak (Infoleak) exploits allow attackers to access sensitive data without authorization. These exploits are typically used to extract information such as encryption keys, memory contents, or login credentials, which attackers can then use to support further exploitation or surveillance. Infoleak exploits are particularly dangerous in shared or multi-tenant environments, where exposed data can compromise multiple users or organizations.

• Example: Spectre-BHB (CVE-2022-23960): This vulnerability affected several modern CPU architectures, allowing attackers to bypass memory isolation protections and access sensitive information stored in protected memory areas. Spectre-BHB posed a severe risk in cloud and virtualized environments, where it could enable attackers to access data across virtual machines in shared infrastructure.

6. Denial of Service (DoS) Exploits

Denial of Service (DoS) exploits aim to disrupt a target service or application, often by overwhelming resources or forcing system crashes. These exploits don’t provide unauthorized access, but they can cause significant operational disruptions. The impact of DoS exploits is often measured in terms of downtime, loss of revenue, and reputational damage, making them especially concerning in industries that rely heavily on continuous service availability.

• Example: SACK Panic (CVE-2019-11477): This vulnerability in the Linux kernel’s TCP stack affects the handling of TCP Selective Acknowledgement (SACK) packets. Specifically, it allows attackers to send crafted SACK packets with a low Maximum Segment Size (MSS), which can trigger a kernel panic and crash the system. Shortly after disclosure, scans and exploitation attempts targeting this vulnerability were observed, particularly against Linux servers in cloud and hosting environments.

The distinctions among exploit types are critical for prioritizing vulnerability remediation. From Initial Access exploits that provide attackers with system entry points to Infoleak and Denial-of-Service exploits that create operational challenges, each type requires tailored mitigation strategies. Understanding these nuances empowers cybersecurity teams to better allocate resources, strengthen defenses, and reduce risks in an increasingly complex threat landscape.