Binary Padding
Adversaries can use binary padding to add junk data and change the on-disk representation of malware without affecting the functionality or behavior of the binary. This will often increase the size of the binary beyond what some security tools are capable of handling due to file size limitations. Binary padding effectively changes the checksum of the file and can also be used to avoid hash-based blacklists and static anti-virus signatures.(Citation: ESET OceanLotus) The padding used is commonly generated by a function to create junk data and then appended to the end or applied to sections of malware.(Citation: Securelist Malware Tricks April 2017) Increasing the file size may decrease the effectiveness of certain tools and detection capabilities that are not designed or configured to scan large files. This may also reduce the likelihood of being collected for analysis. Public file scanning services, such as VirusTotal, limits the maximum size of an uploaded file to be analyzed.(Citation: VirusTotal FAQ)
Mitigations |
|
| Mitigation | Description |
|---|---|
| Binary Padding Mitigation |
Identify potentially malicious software that may be executed from a padded or otherwise obfuscated binary, and audit and/or block it by using whitelisting (Citation: Beechey 2010) tools, like AppLocker, (Citation: Windows Commands JPCERT) (Citation: NSA MS AppLocker) or Software Restriction Policies (Citation: Corio 2008) where appropriate. (Citation: TechNet Applocker vs SRP) |
Detection
Depending on the method used to pad files, a file-based signature may be capable of detecting padding using a scanning or on-access based tool. When executed, the resulting process from padded files may also exhibit other behavior characteristics of being used to conduct an intrusion such as system and network information Discovery or Lateral Movement, which could be used as event indicators that point to the source file.
Связанные риски
Каталоги
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