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)”
Tag Archives: SmartScreen
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”
Attack Techniques: Encrypted Archives
Tricking a user into downloading and opening malware is a common attack technique, and defenders have introduced security scanners to many layers of the ecosystem in an attempt to combat the technique: With all this scanning in place, attackers have great incentives to try to prevent their malicious code from detection up until the momentContinue reading “Attack Techniques: Encrypted Archives”
pushState and URL Blocking
The Web Platform offers a handy API called pushState that allows a website’s JavaScript to change the URL displayed in the address bar to another URL within the same origin without sending a network request and loading a new page. The pushState API is handy because it means that a Web Application can change theContinue reading “pushState and URL Blocking”
Cloaking, Detonation, and Client-side Phishing Detection
Today, most browsers integrate security services that attempt to protect users from phishing attacks: for Microsoft’s Edge, the service is Defender SmartScreen, and for Chrome, Firefox, and many derivatives, it’s Google’s Safe Browsing. URL Reputation services do what you’d expect — they return a reputation based on the URL, and the browser will warn/block loadingContinue reading “Cloaking, Detonation, and Client-side Phishing Detection”
ServiceWorkers vs. Network Filtering
In a recent post, I explored how the design of network security features impact the tradeoffs of the system. In that post, I noted that integrating a URL check directly into the browser provides the security check with the best context, because it allows the client to see the full URL being checked and ifContinue reading “ServiceWorkers vs. Network Filtering”
The Challenge of IP Reputation
When protecting clients and servers against network-based threats, it’s tempting to consider the peer’s network address when deciding whether that peer is trustworthy. Unfortunately, while IP addresses can be a valuable signal, attempts to treat traffic as trustworthy or untrustworthy based on IP address alone can be very prone to mistakes. Background Most clients andContinue reading “The Challenge of IP Reputation”
SmartScreen Application Reputation, with Pictures
Last Update: Sept 3, 2025 I’ve previously explained how Chromium-based browsers assign a “danger level” based on the type of the file, as determined from its extension. Depending on the Danger Level, the browser may warn the user before a file download begins in order to confirm that the user really wanted a potentially-dangerous file.Continue reading “SmartScreen Application Reputation, with Pictures”
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