File metadata-based Yara
To write a file metadata-based Yara rule, you need to specify the metadata characteristics of the files that are associated with the malware that you are trying to detect. Here is an example of a simple file metadata-based Yara rule:
rule example_metadata_rule { condition: file.extension == "exe" and file.size > 100KB }
This Yara rule will match any file that has a “.exe” extension and is larger than 100 KB in size. There are many types of file metadata that you can use in your Yara rules, including the file extension, size, creation, and modification dates, and attributes such as “hidden” or “system.” You can also use logical operators and other syntax elements to create more complex and specific rules. For example, the following rule uses a regular expression to match the file name and a logical operator to specify that the file must have been created within the past 7 days:
rule example_complex_metadata_rule { condition: file.name matches /^malware.*\.exe$/ and file.creation_time > (now - 7d) }
It is important to carefully consider which file metadata characteristics are most relevant for detecting the specific type of malware that you are targeting. You can use multiple metadata characteristics in a single Yara rule to create more specific and sophisticated detection methods.
Threat Hunting Using Yara
Threat hunting is a proactive approach to identifying and mitigating cyber threats that have already entered an organization’s network. It involves actively searching for indicators of compromise (IOC) and signs of malicious activity that may not have been detected by traditional security measures such as antivirus software or firewalls. Threat hunters use a variety of techniques to detect and analyze potential threats, including analyzing log files, network traffic, and system configurations. They may also use tools such as threat intelligence feeds, security incident and event management (SIEM) systems, and malware analysis tools to help identify potential threats. The goal of threat hunting is to detect and mitigate threats as early as possible in the attack life cycle before they can do significant damage. It is an important part of an organization’s overall cybersecurity strategy and can help reduce the risk of successful attacks and data breaches.