SMB Security
SMB security refers to the practices and configurations used to protect the Server Message Block protocol, which enables file sharing, printer access, and inter-process communication in Windows networks, from exploitation and unauthorized access.
The Server Message Block (SMB) protocol is essential for file and resource sharing in Windows environments. However, its long history and widespread deployment have made it a frequent target for attackers. The EternalBlue exploit (CVE-2017-0144), which targeted SMBv1, enabled the devastating WannaCry and NotPetya ransomware campaigns. SMB relay attacks exploit authentication handshakes to gain unauthorized access to network resources.
SMB has evolved through several versions, with SMBv3 offering significant security improvements including encryption, secure negotiation, and pre-authentication integrity checks. Despite these advances, legacy SMBv1 remains enabled on many networks, creating significant vulnerability. Attackers also exploit SMB for credential harvesting by tricking systems into authenticating to malicious servers, capturing NTLM hashes for offline cracking.
Securing SMB requires disabling SMBv1 across all systems, enforcing SMB signing to prevent relay attacks, enabling SMBv3 encryption for sensitive shares, restricting SMB traffic through firewall rules to only necessary network segments, implementing strong access controls on shared resources, and monitoring for anomalous SMB activity. Organizations should audit exposed SMB shares regularly and ensure that sensitive data is not inadvertently accessible through misconfigured permissions.