- Some applications, especially ones that are geographically based, are not digitally signed (yet) by their manufacturers and they are executed from %APPDATA% (C:\Users\*\AppData\Local\ or C:\Users\*\AppData\LocalLow\). While creating a simple wildcard passive Path Rule allows them to execute, it also can allow ransomware like TeslaCrypt to execute as well. The best recommendation is to identify each of the applications that need to execute from these locations and create Hash Rules. Hopefully, your environment only has a couple of applications that fall into this category, and we strongly recommend contacting each of these vendors and request they begin digitally signing their applications. Then, a simple Publisher can properly solve the execution issue with whatever privileges are needed.
- To ensure everything is working correctly, the Deny Rule should always be the last in the rule list. All passive and privilege rules should process first and then anything that has not matched will be denied.
- If there is a desire to block / deny applications before the last Deny Rule, consider applying rules to specific applications, paths, and temporary directories (i.e. c:\ or C:\windows\temp\).
- To ensure the best user experience, keep the rule base small, around 50 rules maximum. This will keep the performance optimized with minimal or no impact to the end user.
- All acceptable applications should have passive rules by Publisher (preferred and best practice) or a global path and subdirectory. Remember to include child applications when necessary. For example, “C:\Program Files\Custom Applications\*” as a passive rule with all children.
- If multiple applications that are unsigned and in various directories are installed, rules will be needed for each. Standardizing on a trusted directory structure would help minimize the number of rules and places malware can be deposited and executed on the system.
Morey J. Haber, Chief Technology Officer and Chief Information Security Officer at BeyondTrust
Morey J. Haber is Chief Technology Officer and Chief Information Security Officer at BeyondTrust. He has more than 25 years of IT industry experience and has authored four Apress books: Privileged Attack Vectors (2 Editions), Asset Attack Vectors, and Identity Attack Vectors. In 2018, Bomgar acquired BeyondTrust and retained the BeyondTrust name. He originally joined BeyondTrust in 2012 as a part of the eEye Digital Security acquisition. Morey currently oversees BeyondTrust strategy for privileged access management and remote access solutions. In 2004, he joined eEye as Director of Security Engineering and was responsible for strategic business discussions and vulnerability management architectures in Fortune 500 clients. Prior to eEye, he was Development Manager for Computer Associates, Inc. (CA), responsible for new product beta cycles and named customer accounts. He began his career as Reliability and Maintainability Engineer for a government contractor building flight and training simulators. He earned a Bachelor of Science degree in Electrical Engineering from the State University of New York at Stony Brook.