An attack known as Pass the Hash has been targeting Windows machines since the days of Windows 3.11, but Colombian security researcher Juan Diego recently discovered that a threat actor could easily obtain NT LAN Manager (NTLM) password hashes without any user intervention.

How the Attack Works

The attack itself is rather simple: A Shell Command File (SCF) is placed in a public folder with no password protection. These are plaintext files that instruct Windows File Explorer to execute basic tasks.

For some reason, the SCF file is executed as soon as it is placed in the folder. It then sucks up the NTLM password hash and sends it to the attacker’s server. At that point, the threat actor can decrypt the hash and the password to gain access to the victim’s machine.

“This [attack] is automatic. The underlying issue triggering this is still unknown to me. [Microsoft] has been very secretive about that,” Diego told Bleeping Computer.

This is a departure from previous exploits, which began only after the victim had accessed the poisoned folder. One recent attack combined a Chrome extension with SCF files to gain a user’s credentials.

Protecting NTLM Passwords

The Pass the Hash attack arose from the automatic sharing of NTLM hashes with servers that are located outside of the original network. This is a long-standing architectural flaw in Windows that Microsoft has been reluctant to discuss or fix.

The technology giant did issue an optional patch (ADV170014) that disables the scheme by changing two registry keys and prevents fraudsters from duping users into authenticating on servers outside their local network. However, the fix only works on Windows 10 and Windows Server 2016, and Microsoft has not announced any plans to extend the patch to previous versions.

A simpler solution is to use password-protected public folders. The benefit of avoiding this type of attack far outweighs the slight inconvenience of having to enter a password to gain access.

More from

New Attack Targets Online Customer Service Channels

An unknown attacker group is targeting customer service agents at gambling and gaming companies with a new malware effort. Known as IceBreaker, the code is capable of stealing passwords and cookies, exfiltrating files, taking screenshots and running custom VBS scripts. While these are fairly standard functions, what sets IceBreaker apart is its infection vector. Malicious actors are leveraging the helpful nature of customer service agents to deliver their payload and drive the infection process. Here’s a look at how IceBreaker…

Operational Technology: The evolving threats that might shift regulatory policy

Listen to this podcast on Apple Podcasts, Spotify or wherever you find your favorite audio content. Attacks on Operational Technology (OT) and Industrial Control Systems (ICS) grabbed the headlines more often in 2022 — a direct result of Russia’s invasion of Ukraine sparking a growing willingness on behalf of criminals to target the ICS of critical infrastructure. Conversations about what could happen if these kinds of systems were compromised were once relegated to “what ifs” and disaster movie scripts. But those days are…

Cybersecurity 101: What is Attack Surface Management?

There were over 4,100 publicly disclosed data breaches in 2022, exposing about 22 billion records. Criminals can use stolen data for identity theft, financial fraud or to launch ransomware attacks. While these threats loom large on the horizon, attack surface management (ASM) seeks to combat them. ASM is a cybersecurity approach that continuously monitors an organization’s IT infrastructure to identify and remediate potential points of attack. Here’s how it can give your organization an edge. Understanding Attack Surface Management Here…

Six Ways to Secure Your Organization on a Smaller Budget

My LinkedIn feed has been filled with connections announcing they have been laid off and are looking for work. While it seems that no industry has been spared from uncertainty, my feed suggests tech has been hit the hardest. Headlines confirm my anecdotal experience. Many companies must now protect their systems from more sophisticated threats with fewer resources — both human and technical. Cobalt’s 2022 The State of Pentesting Report found that 90% of short-staffed teams are struggling to monitor…