What Is Cache Poisoning?
Cache poisoning is a cybersecurity attack that targets cache storage systems to distribute malicious data to unsuspecting users. Caches, which store temporary copies of data for quick access, are found in various parts of the internet infrastructure, including DNS servers and web servers. When an attacker successfully poisons a cache, they can alter the data that users receive, redirecting them to fraudulent websites, injecting malware, or stealing personal information. This type of attack exploits the fundamental way caches operate, leveraging their efficiency mechanisms for malicious purposes.
Cache poisoning attacks undermine the integrity and trustworthiness of the internet. They manipulate the expected behavior of caching mechanisms to serve malicious content or redirect traffic without the knowledge or consent of the end-user. This can have wide-ranging implications, from individual security breaches to large-scale disruptions of internet services, making it a critical concern for cybersecurity professionals.
This is part of a series of articles about DDoS
In this article:
- Types of Cache Poisoning and How They Work
- Risks Associated with DNS Cache Poisoning
- 3 Ways to Prevent DNS Cache Poisoning
- Risks Associated with Web Cache Poisoning
- 4 Ways to Prevent Web Cache Poisoning
Types of Cache Poisoning and How They Work
DNS Cache Poisoning
DNS cache poisoning, also known as DNS spoofing, targets the Domain Name System, which translates domain names into IP addresses. By injecting false DNS information into a resolver’s cache, attackers can redirect users to malicious sites without their knowledge. This attack exploits the trust relationship between clients and DNS servers, allowing attackers to impersonate legitimate sites and capture sensitive information.
To execute DNS cache poisoning, attackers send fraudulent responses to DNS queries before the legitimate response arrives. If a poisoned DNS entry is cached, all subsequent requests for that domain lead to the attacker-controlled IP address. Successful DNS cache poisoning can lead to widespread disruption, as users are unknowingly redirected to phishing or malware sites.
Related content: Read our guide to DNS Flood
How DNS poisoning works (Source)
Web Cache Poisoning
Web cache poisoning involves manipulating the caching mechanism of web applications to serve malicious content. Attackers exploit vulnerabilities in the application’s handling of HTTP requests and responses. By sending a specially crafted request that the application processes incorrectly but still caches, attackers can inject harmful content into the cache. Subsequent users requesting the same resource receive the poisoned content, leading to potential security breaches.
This method relies on the complexity and variability of web applications. Many factors, such as how inputs are processed and how content is dynamically generated, can create opportunities for poisoning. Attackers exploit these vulnerabilities by understanding the specific behaviors of web caches and crafting requests that bypass normal security checks but are still accepted and cached.
How web cache poisoning works (Source)
Risks Associated with DNS Cache Poisoning
Malware Infection
DNS cache poisoning can lead to widespread malware infection. By redirecting users to malicious sites, attackers can easily deploy malware onto end-user devices. The infection can spread rapidly, especially when popular websites are affected. Once infected, devices can become part of botnets or be subject to ransomware attacks. The repercussions are significant, including data loss, compromised security, and financial damages.
Data Theft
DNS cache poisoning can facilitate data theft. Redirecting users to fraudulent sites allows attackers to phish for sensitive information. Users, believing they’re on legitimate sites, might enter personal or financial information, which can lead to data theft, financial theft, or identity theft. The stolen data can be used for various malicious purposes, including unauthorized transactions, blackmail, or selling the information on the dark web.
Interfering with Security Updates
DNS cache poisoning can interfere with security updates. Users might be redirected away from legitimate update sites to malicious ones offering fake updates. These fake updates could contain malware, further compromising users’ systems.
Such interference undermines software integrity and exposes users to vulnerabilities that genuine updates would have fixed. The delay or prevention of critical updates poses a significant security risk.
3 Ways to Prevent DNS Cache Poisoning
1. Deploy DNS Security Extensions
DNSSEC (DNS Security Extensions) provides a layer of security for the DNS. It uses digital signatures to verify the authenticity of response data. Implementing DNSSEC can prevent attackers from inserting falsified information into the DNS cache.
DNSSEC ensures that users are directed to the correct IP addresses, protecting them from malicious redirects. However, it requires some effort from domain owners and ISPs to implement.
2. Use End-to-End Encryption
End-to-end encryption, which can be implemented via the HTTPS protocol, secures communication between users and websites. By encrypting data, it prevents attackers from intercepting or altering information, including DNS queries and responses.
Encryption makes it significantly more challenging for attackers to implement DNS cache poisoning. However, users and websites must support encryption for it to be effective, highlighting the importance of HTTPS adoption.
3. Deploying DNS Spoofing Detection Tools
Deploying DNS spoofing detection tools is an effective method for identifying and mitigating DNS cache poisoning attacks. These tools monitor DNS traffic for suspicious patterns, such as unusually rapid responses or responses from unexpected IP addresses. By analyzing DNS queries and responses in real-time, these tools can detect anomalies that indicate a poisoning attempt.
Furthermore, DNS spoofing detection tools can be integrated with other security systems, such as intrusion detection systems (IDS) and security information and event management (SIEM) systems. By correlating data from various sources, organizations can better understand attack patterns and strengthen their defenses against DNS cache poisoning.
Risks Associated with Web Cache Poisoning
Spread of Malicious Content
Web cache poisoning facilitates the spread of malicious content by exploiting the trust users have in legitimate websites. When attackers poison a web cache, they can insert harmful scripts, malware, or phishing pages that are then served to unsuspecting users. This not only endangers the security of end users but also harms the reputation of the affected websites.
Denial of Service
Web cache poisoning can also be used to conduct denial of service (DoS) attacks. By inserting resource-intensive pages or broken links into the cache, attackers can cause legitimate pages to become inaccessible. This not only disrupts the availability of the website for users but can also overload the web server.
Bypassing Security Controls
Another risk associated with web cache poisoning is the ability to bypass security controls. By manipulating cached content, attackers can circumvent website security measures designed to protect against XSS (Cross-Site Scripting), CSRF (Cross-Site Request Forgery), and other web-based attacks. This can expose users to a wide range of security threats, including unauthorized access to sensitive information and session hijacking.
4 Ways to Prevent Web Cache Poisoning
1. Cache Key Normalization
Cache key normalization standardizes the processing of HTTP requests. By removing variability in how requests are handled, it limits the exploitation of the caching mechanism. This technique makes it harder for attackers to inject or alter cached content.
Normalization focuses on treating similar requests as identical, reducing the opportunities for cache poisoning. It’s a proactive measure that enhances the resilience of web caching systems.
2. Cache-Control Headers
Cache-Control headers play a crucial role in defining caching policies for web applications. By specifying directives in the HTTP headers, web developers can control how and whether caching mechanisms should store the responses.
For example, setting Cache-Control: no-store instructs caches not to store a copy of the given response. Cache-Control: private ensures the response is stored only in private caches (like a user’s browser), not in shared caches (like an ISP or CDN cache), which could be more vulnerable to poisoning attacks. By configuring these headers, developers can reduce the risk of poisoning, ensuring that only intended, unaltered content is delivered to the end-user.
3. Validate User Input
Validating user input is a critical defense mechanism against web cache poisoning. This process involves checking and sanitizing any data received from users before it’s processed by the web application or stored in the cache. The goal is to ensure that only valid, expected data is accepted, thereby preventing attackers from injecting malicious content through crafted requests.
Input validation can block attempts to exploit vulnerabilities in the application’s logic that might lead to cache poisoning, such as unexpected combinations of parameters or malformed URLs. Effective input validation requires an allowlist approach, where only known, safe input patterns are accepted. This might include strict type checking, length verification, and pattern matching against regular expressions.
4. Use Web Application Firewalls (WAF)
Web Application Firewalls (WAFs) are an essential security layer for defending against web cache poisoning and other web-based threats. A WAF operates by inspecting incoming web traffic and filtering out malicious requests based on predefined or dynamic rulesets. By positioning a WAF between the internet and the web application, it acts as a gatekeeper, preventing harmful requests from reaching the server or corrupting the cache.
To counter web cache poisoning, WAFs can be configured to detect and block requests that attempt to exploit known vulnerabilities or exhibit patterns indicative of an attack. This includes unusual query parameters, unexpected HTTP headers, or anomalous request paths. Moreover, WAFs can be updated regularly with new rules to adapt to emerging threats, providing an evolving defense mechanism.
Cache Poisoning Protection with Imperva
Imperva provides a Web Application Firewall, which can prevent cache poisoning and thousands of other attacks with world-class analysis of web traffic to your applications.
Beyond the WAF, Imperva provides comprehensive protection for applications, APIs, and microservices:
Runtime Application Self-Protection (RASP) – Real-time attack detection and prevention from your application runtime environment goes wherever your applications go. Stop external attacks and injections and reduce your vulnerability backlog.
API Security – Automated API protection ensures your API endpoints are protected as they are published, shielding your applications from exploitation.
Advanced Bot Protection – Prevent business logic attacks from all access points – websites, mobile apps and APIs. Gain seamless visibility and control over bot traffic to stop online fraud through account takeover or competitive price scraping.
DDoS Protection – Block attack traffic at the edge to ensure business continuity with guaranteed uptime and no performance impact. Secure your on premises or cloud-based assets – whether you’re hosted in AWS, Microsoft Azure, or Google Public Cloud.
Attack Analytics – Ensures complete visibility with machine learning and domain expertise across the application security stack to reveal patterns in the noise and detect application attacks, enabling you to isolate and prevent attack campaigns.
Client-Side Protection – Gain visibility and control over third-party JavaScript code to reduce the risk of supply chain fraud, prevent data breaches, and client-side attacks.
