Researchers have demonstrated a proof-of-concept technique called BigDiskBuster that interferes with Microsoft Defender's ability to refresh its virus definitions. The security service itself keeps running, so the system appears healthy to administrators and users, but the update process is effectively blocked.
The approach does not rely on an exploit or a known vulnerability, which makes it a potentially attractive tool in an attacker's arsenal. While the article notes that this is not quite an EDR-killer, it still undermines a core layer of endpoint protection by leaving a silent window in which malicious files may go undetected.
Because Defender appears operational, the gap could persist until someone manually verifies that the latest definitions have been applied. The finding highlights how security tools can be weakened without being fully disabled, and it reinforces the importance of monitoring update integrity rather than only service status.