Microsoft‘s own built-in antivirus system slowly skyrocketing in the antivirus market. However, Microsoft actually unintentionally releases a faulty update known as, Security Intelligence Signature KB2310138 (Version 1.313.1638.0), that eventually causes the Windows Security (Windows Defender) system to crash back on Thursday. This update causes a technical glitch where, Windows Defender stops responding and freezes when a scan schedule is being operated.
Apparently, on the very next day, Microsoft patches the faulty update with a newer signature coded as KB2310138 (Version 1.313.1734.0) that solves the problem once and for all. You can patch the bug with a newer signature issued to Windows Defender either through the manual way or through a Windows Update.