Burp Comparer is an indispensable tool within Burp Suite Professional, designed to meticulously analyze and highlight differences between any two pieces of data. As a powerful comparer, it empowers security professionals and web developers to efficiently pinpoint subtle variations in web requests and responses, significantly streamlining vulnerability analysis and security testing workflows.
For instance, when performing tasks such as username enumeration, Burp Comparer excels at contrasting responses from failed login attempts using both valid and invalid usernames. This capability is crucial for identifying potential vulnerabilities. Similarly, when dealing with large responses of varying lengths, often encountered during Intruder attacks, the comparer function helps to quickly discern critical differences. It is also invaluable for comparing similar requests that yield divergent application behaviors, aiding in understanding application logic and identifying anomalies. Furthermore, when testing for blind SQL injection vulnerabilities using Boolean condition injection, the comparer is essential for determining if injecting different conditions leads to discernible variations in server responses, a key indicator of vulnerabilities.
Step-by-Step Guide to Using Burp Comparer
Leveraging Burp Comparer for your web security tasks is straightforward. Follow these steps to effectively utilize this comparer tool:
- Identify Target Messages: Begin by locating the specific requests or responses within Burp Suite that you intend to analyze. These could be intercepted requests in the Proxy history, Intruder attack results, or any other data within Burp Suite.
- Send to Comparer: Right-click on each of the messages you wish to compare. From the context menu, select “Send to Comparer”. You can send messages from virtually any tool within Burp Suite, making it a highly accessible comparer.
- Access the Comparer Tab: Navigate to the “Comparer” tab in the Burp Suite interface. Here, you will find two item tables populated with the messages you’ve sent.
- Select Items for Comparison: Within each table, select the two messages you want to juxtapose using the comparer.
- Choose Comparison Type: Decide on the comparison method. Click either “Words” for a word-level analysis or “Bytes” for a byte-level comparison. Upon selection, a new window will appear displaying the comparison results, highlighting the differences identified by the comparer.
It’s important to note that each item table serves as a repository of all messages sent to the comparer. You must select one item from each table to initiate the comparison process. To organize the messages within the tables, you can click on any table header to sort the contents according to that header.
Understanding Comparer Controls
The Burp Comparer tab is equipped with several intuitive controls to manage and analyze your data effectively. These controls enhance the functionality of the comparer, providing flexibility in data input and manipulation:
- Paste: This function allows you to add data directly from your clipboard into the comparer. Simply copy the text you want to compare and use the “Paste” button to add it as a new item.
- Load: The “Load” control enables you to import data from a file. This is particularly useful when dealing with large datasets or logs that are stored externally.
- Remove: To delete a specific item from the comparer, highlight the item and click “Remove”. This helps in decluttering your workspace and focusing on relevant comparisons.
- Clear: The “Clear” button provides a quick way to delete all items from both item tables, allowing you to start fresh with new comparisons.
Burp Comparer offers two distinct analysis options, catering to different levels of comparison granularity:
- Words: The “Words” option performs a word-level comparison. This method tokenizes the data based on whitespace delimiters and identifies the modifications needed at the word level to transform the first item into the second. It is efficient for understanding high-level textual changes.
- Bytes: For a more granular analysis, the “Bytes” option conducts a byte-level comparison. This identifies every byte-level edit required to transform one item into another. While more computationally intensive, it is invaluable for pinpointing subtle, byte-specific differences that might be missed in a word-level comparison. It is generally recommended to use byte-level comparison when word-level analysis fails to highlight the necessary distinctions.
Interpreting Comparer Results
The results of your comparison are displayed in a new window, presenting the compared items side-by-side in two panels. Burp Comparer uses intuitive color-coding to visually represent the differences: modifications, deletions, and additions are clearly highlighted, making it easy to grasp the variations at a glance. Text that remains unhighlighted indicates identical sections present in both compared items.
The title bar of the results window conveniently displays the total number of differences detected by the comparer, providing a quantitative summary of the analysis.
To further aid in result analysis, the results window includes several helpful controls:
- Sync views: Enabling “Sync views” synchronizes the scrolling of both panels. This is particularly useful when comparing large items, ensuring that you are always viewing corresponding sections of both items simultaneously.
- Text: The “Text” view displays both items in their textual format, making it easy to read and understand the content being compared.
- Hex: For low-level analysis, the “Hex” view presents both items in hexadecimal format. This is crucial when you need to examine byte-level data or non-textual content.
Expanding Your Comparison Capabilities within Burp Suite
Beyond comparing arbitrary data, Burp Suite extends its comparison capabilities to specific tools like the Site map. The comparer functionality is also integrated within the Target > Site map tab, allowing you to compare two site maps. This feature is detailed in Comparing site maps, offering another dimension to your web security analysis toolkit.
By mastering Burp Comparer, you significantly enhance your ability to identify and understand differences in web traffic, making it an essential tool for effective web security testing and vulnerability analysis. Its versatility as a comparer for various types of data within Burp Suite makes it a cornerstone of efficient security workflows.
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