In the realm of computer security, static analysis plays a crucial role in detecting viruses and malware. Unlike dynamic analysis, which involves running code to observe its behavior, static analysis involves examining files or records for the presence of virus patterns without executing any code. This article explores various static detection methods used to identify viruses and protect computer systems from potential threats.
1. String Scanning Method:
The string scanning method is one of the fundamental techniques employed in static detection. It searches for specific sequences of bytes, known as strings, that are characteristic of a particular virus. By comparing these strings against a database of known virus patterns, the detection software can identify potential threats. These strings are carefully chosen to be unique to viruses and unlikely to be found in legitimate programs.
2. Wildcards Method:
The wildcards method introduces flexibility into the detection process. It allows the scanner to skip certain bytes or byte ranges while searching for virus patterns. For example, the “?” wildcard character can be used to skip bytes, and the “%” wildcard can be used to match the next byte. This method enables the detection software to accommodate slight variations in the virus’s code structure.
3. Mismatches Method:
The mismatches method offers further adaptability in virus detection. It permits a certain number of bytes within a string to have arbitrary values, regardless of their position. This approach accounts for potential modifications made by virus creators to evade detection. By tolerating a limited number of mismatches, the scanner can still identify viruses with slight variations in their code.
4. Generic Detection Method:
The generic detection method utilizes a common string to detect multiple or all known variants of a virus family. Instead of relying on specific strings associated with each variant, this technique employs a generic string that is common to all members of the virus family. By using a shared characteristic, the detection software can effectively identify a broader range of threats.
5. Bookmarks Method:
The bookmarks method involves calculating the distance between the start of the virus body and the detection string. This approach helps pinpoint the exact location of the virus within a file. By determining this distance accurately, the detection software can effectively locate and isolate the virus code.
6. Smart Scanning:
Smart scanning takes into account the structure of the host file and skips unnecessary instructions, such as NOPs (no-operation instructions). It also avoids storing these instructions in the virus signature, reducing false positives. Additionally, smart scanning identifies an area within the virus body that lacks references to data or other subroutines. By focusing on this isolated area, the scanner increases the likelihood of detecting related variants of viruses.
7. Skeleton Detection:
Skeleton detection targets macro viruses, which often contain nonessential statements. The scanner parses the statements of the virus line-by-line, removing any nonessential code. This process leaves behind only the essential macro code common to most macro viruses. By focusing solely on the core functionality, the scanner improves the efficiency of detection.
8. Heuristics Analysis:
Heuristic analysis involves expert-based analysis to determine the vulnerability of a system to specific threats. Decision rules or weighing methods are used to assess the risk posed by a particular virus or malware. MultiCriteria analysis (MCA) is one such technique that aids in weighing and evaluating the various criteria involved in the analysis.
9. Virus-Specific Detection:
In cases where standard virus scanning algorithms are insufficient, virus-specific detection methods are employed. This approach involves implementing a new detection code to address a specific virus that cannot be handled by conventional techniques. Virus-specific detection may include filtering mechanisms, decryptor detection, and x-ray scanning to uncover hidden or complex virus structures.
In conclusion, static detection methods are invaluable in combating viruses and malware. By employing various techniques such as string scanning, wildcards, mismatches, generic detection, bookmarks, smart scanning, skeleton detection, heuristics analysis, and virus-specific detection, security professionals can effectively identify and neutralize potential threats. These methods play a vital role in safeguarding computer systems and protecting against the ever-evolving landscape of cyber threats.