URL Base64 Decoding for Suspicious Link Detection
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Solution Overview
Problem
Existing methods for decoding Base64 encoded data in URLs are incomplete and fail to detect suspicious URLs effectively, particularly when attackers hide telltale information in various parts of the URL using the Base64 encoding scheme.
Innovation Solution
A method to detect suspicious URLs by searching for the longest possible Base64 substrings in the URL's path, query, and fragment, converting them to binary data, and then to ASCII strings, and evaluating the information type using regular expressions to identify potential threats such as email addresses, phone numbers, or credit card numbers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Base64 decoding is performed only on the fragment part of the URL, then the decoding process is simple, but the detection is incomplete and fails to detect suspicious URLs in other parts
Solution Approach 1:
The URL is divided into multiple segments (path, query parameters, and fragment) for separate Base64 decoding analysis. Each segment is processed independently to identify suspicious encoded information, ensuring comprehensive detection while maintaining manageable complexity through systematic segmentation of the decoding task.
2Reliability
If the entire URL is decoded using Base64, then all suspicious information can be detected, but the decoding process becomes computationally expensive and time-consuming
Solution Approach 1:
Instead of decoding the entire URL, only specific segments (path, query, fragment) that are likely to contain suspicious Base64 encoded information are decoded. This partial action approach maintains high detection accuracy for suspicious URLs while significantly reducing the computational time and resources required compared to full URL decoding.
3Object-affected harmful factors
If Base64 encoded sensitive information is hidden in URLs, then attackers can evade detection, but cybersecurity systems fail to identify threats
Solution Approach 1:
The system converts the harmful obfuscation technique (Base64 encoding used by attackers) into a beneficial detection mechanism by implementing Base64 decoding capabilities. This allows the cybersecurity system to identify and flag suspicious URLs that contain encoded sensitive information such as email addresses, credit card numbers, and other PII, transforming the attacker's evasion method into a detectable pattern.
Data Source
AI summary
A suspicious Uniform Resource Locator (URL) of a resource on the public Internet is detected by searching a part of the URL for a candidate substring, which is the longest possible substring that is in accordance with a Base64 encoding scheme. The candidate substring is converted to a candidate binary data in accordance with the Base64 encoding scheme. The candidate binary data is then converted to a candidate American Standard Code for Information Interchange (ASCII) string. The candidate ASCII string is evaluated to determine the information type of the candidate ASCII string. A determination as to whether the URL is suspicious is based at least on the information type of the candidate ASCII string.