Reliability and Issues of Microsoft Defender

Although presented as a standard Windows application, Microsoft Defender is often considered an excellent solution for malware protection. Threat detection evaluations by AV-Comparatives and AV-TEST prove that Defender performs well compared to third-party solutions. However, this security software is not flawless and can sometimes give false alarms. In the past, it has been observed marking Office updates as malware, Google Chrome updates as ‘suspicious,’ and legitimate URLs and links as viruses. Recently, it was found to block the loading of Edge’s websites, which was determined to be due to a new feature removed from Defender. Microsoft stated in a 2022 announcement that they have improved their methods to reduce false positives and negatives, acknowledging that there is still much work to be done.

The Case of Microsoft Defender Flagging as Casdet Trojan

And now, a user named X, a yappy user, noticed that Defender flags it when trying to save a text file with the content “This content is no longer available.“. When trying to save this to a TXT file, Defender considers it a Casdet trojan and marks it as a serious threat, identifying it as “Trojan:Win32/Casdet!rfn“. Initially, user X thought this was due to a SHA-256 collision, but the source of the problem seems different. Although the explanation on Microsoft’s official website does not clarify this issue much, it can be said that it is not a major problem as it does not cause Windows to crash. Nonetheless, we hope that Microsoft will resolve this issue soon.