How Cybersecurity Experts Crack Passwords with Burp Suite

Summary

Sources

portswigger.net

In the world of cybersecurity, the digital battleground is every bit as intense as any physical conflict. The pressing challenge of gaining unauthorized access to accounts through brute-forcing passwords stands as a testament to this statement. Burp Suite emerges as a comprehensive platform for web security testing, offering users the tools to perform dictionary and exhaustive brute-force attacks. Burp Suite's features facilitate the brute-force of passwords, enabling access to a user's account and widening the attack surface. For instance, it allows the use of a list of common passwords, a strategy known as a dictionary attack, or to try every permutation of a character set. It's important to note that while these examples are simplified to demonstrate how to use Burp Suite's features, real-world scenarios often require bypassing additional defenses like rate limiting. Before initiating a brute-force attack, it is critical to identify valid usernames for the target website. Usernames can be enumerated using Burp Suite itself, and for the following examples, the username 'wiener' is considered valid. In a dictionary attack, a list of potential passwords, typically sourced from previous data breaches, is employed. This method is considerably more efficient than an exhaustive brute-force attack, but it hinges on the password being included in the list. To set up a dictionary attack using Burp Suite, the initial step involves sending the login request to Burp Intruder. By selecting the Sniper attack type and marking the password value as a payload position, users input a list of passwords to be tested, prioritizing them based on likelihood. Burp Suite Professional offers the convenience of a built-in 'Passwords' list, while the Community Edition requires manual list input. Once the attack is launched, responses must be scrutinized for indications of a successful breach, such as unusual error messages, response times, or status codes. In contrast, an exhaustive brute-force attack involves attempting every possible permutation of a character set. This method can potentially brute-force passwords not found in any wordlist, but is limited by the sheer number of necessary requests, making it less viable for longer passwords. An alphabetical password with a length of five characters alone has over eleven million combinations. Preceding an exhaustive attack with a dictionary attack is often a more strategic approach. After sending the login request to Burp Intruder and marking the password value, users configure the full character set and password length settings. By starting the attack, Burp Intruder will cycle through every possible password permutation, and similar to the dictionary attack, the responses must be examined for signs of a valid password. Both approaches underscore the necessity of analyzing the responses to pinpoint a valid password. The use of Burp Suite's Comparer tool is instrumental in this process, highlighting differences between the responses and helping to identify successful password breaches. Whether through a dictionary or exhaustive brute-force attack, Burp Suite stands as a critical tool in the cybersecurity arsenal, enabling users to navigate the complex and demanding realm of web security testing. Turning the focus to the dictionary attack, this technique utilizes a list of commonly used passwords, with the assumption that a significant number of users continue to depend on easily guessable or previously exposed passwords. The process of setting up a dictionary attack using Burp Suite involves a series of systematic steps. Firstly, the login request must be captured, which is done by sending the request for submitting the login form to Burp Intruder. Once in Burp Intruder's Positions tab, the Sniper attack type is selected. The password value is then highlighted and marked as a payload position using the 'Add §' function, ensuring that a valid username is in use for the attack. The next phase is to select and input a list of potential passwords into the Payloads tab, under 'Payload settings [Simple list].' It's crucial to prioritize this list, arranging the passwords by the likelihood of their accuracy. The selection could be informed by known user habits or the general frequency of password use. For users of Burp Suite Professional, a built-in list named 'Passwords' can be leveraged, streamlining the process. After initiating the attack, Burp Intruder sends a request for each password on the list. Upon completion, the responses require close examination for anomalies that suggest a valid password has been used. This could manifest as unique error messages, varying response times, or specific status codes. An example would be receiving a 302 response, which typically indicates a redirection, often after successful authentication. To analyze the responses, they can be sent to Burp's Comparer tool, where differences are highlighted, aiding in the identification of a successful breach. The selection of the right password list is paramount as it can significantly reduce the time and resources spent on the attack. An effective list increases the probability of a match, making the dictionary attack a potent tool for breaching accounts with less secure passwords. The analysis of responses is equally important, as it confirms the success of the attack, allowing the attacker to move forward in their security testing or exploitation efforts. Understanding and executing a dictionary attack in Burp Suite thus requires not only the technical know-how of setting up the attack but also the analytical acumen to interpret the results, drawing a line between a failed attempt and an unauthorized entry into an account. Advancing from the dictionary attack, the exhaustive brute-force attack represents a more extensive approach by testing every possible combination of characters from a specified set. This method, while comprehensive, is known for being incredibly resource-intensive. The time and computational power required grow exponentially with the increase in password length, rendering it impractical for cracking longer passwords. To set up an exhaustive brute-force attack in Burp Suite, the process begins in a similar fashion to the dictionary attack—by sending the target login request to Burp Intruder. After highlighting the password field and marking it as a payload position, the focus shifts to the Payloads tab. Here, under the category of 'Payload sets,' the 'Brute forcer' payload type is selected. Next, users must define the full character set they wish to use in the 'Payload settings [Brute forcer].' Additionally, the minimum and maximum lengths of the password are set, which helps to narrow down the scope of the attack based on the known or assumed password policies of the website in question. A savvy attacker may create an account on the target site to gain insights into the password requirements, thus tailoring the brute-force attack more effectively. Once the attack is launched, Burp Intruder will tirelessly send requests, each one representing a different password permutation based on the defined character set and length. As the attack unfolds, responses need to be monitored and analyzed for any indication of a successful login, often revealed through deviations in error messages, response times, or status codes. The exhaustive nature of this method, however, comes with significant limitations. The number of permutations can swiftly reach astronomical figures, making the task daunting without the aid of substantial computational resources. For this reason, understanding the website's password requirements is not merely beneficial but essential for an efficient attack. By incorporating this knowledge, the range of permutations can be strategically reduced, thereby increasing the likelihood of identifying the correct password within a reasonable timeframe. Yet, despite these challenges, the exhaustive brute-force attack remains a valuable technique within the arsenal of cybersecurity tools. When employed judiciously and with due consideration of its limitations, it holds the potential to unlock accounts safeguarded by non-dictionary passwords, providing a testament to the resilience and adaptability of security testing methods in the face of evolving digital defenses.