Security Software False Positives

Software developers and end-users are often interested in understanding how to resolve incorrect detections from their antivirus/security software, including Microsoft Defender. Such False Positives (FPs) can disrupt your use of your device by incorrectly blocking innocuous files or processes. However, you should take extreme care before concluding that a given detection is a false positiveContinue reading “Security Software False Positives”

Attack Techniques: Fake Literally Everything! (Escrow Scam)

The team recently got a false-negative report on the SmartScreen phishing filter complaining that we fail to block firstline-trucking.com. I passed it along to our graders but then took a closer look myself. I figured that maybe the legit site was probably at a very similar domain name, e.g. firstlinetrucking.com or something, but no suchContinue reading “Attack Techniques: Fake Literally Everything! (Escrow Scam)”

Understanding SmartScreen and Network Protection

The vast majority of cyberthreats arrive via one of two related sources: That means that by combining network-level sensors and throttles with threat intelligence (about attacker sites), security software can block a huge percentage of threats. Protection Implementation On Windows systems, that source of network threat information is commonly called SmartScreen, and support for queryingContinue reading “Understanding SmartScreen and Network Protection”

Runtime Signature Checking Threat Model

Telerik developers recently changed Fiddler to validate the signature on extension assemblies before they load. If the assembly is unsigned, the user is presented with the following message: In theory, this seems fine/good– signing files is a good thing! However, it’s important to understand the threat model and tradeoffs here. Validating signatures every time aContinue reading “Runtime Signature Checking Threat Model”

Best Practices for SmartScreen AppRep

Last year, I wrote about how Windows integrates SmartScreen Application Reputation to help ensure users have a secure and smooth experience when running downloaded software. tl;dr: When a user runs a downloaded program, a call to SmartScreen’s web-based reputation service is made, and four possible outcomes can occur: As a software developer, it’s natural thatContinue reading “Best Practices for SmartScreen AppRep”