A fileless attack is leveraging PCASTLE to distribute samples of XMRig, a well-known Monero-mining malware family.

Trend Micro first observed the campaign on May 17 when it spotted a series of attacks targeting systems based in China. These attacks, which peaked on May 22 before leveling off, used a scheduled task or RunOnce registry key to download the first-stage PowerShell script. The script then searched for a URL inside of itself to download, execute and save a PowerShell command as a scheduled task.

At this stage in the infection chain, the scheduled task launched a PowerShell script that downloaded and executed the attacks’ second-stage PowerShell script. This asset then collected and reported system information to its command-and-control (C&C) server before downloading the third-stage PowerShell script. At this point, the attacks leveraged PCASTLE, an obfuscated PowerShell script to be used in additional propagation efforts and an XMRig module.

A Brief History of PCASTLE and XMRig Activity

XMRig has been a popular code base for cryptomining since the rise of this type of threat in mid-2017. In May 2018, ThreatPost reported on a new malware strain called WinstarNssmMiner that dropped XMRig as an additional payload under certain circumstances. A few months earlier, Palo Alto Networks found a large-scale operation that exposed as many as 15 million people to XMRig over a four-month period.

Both PCASTLE and XMRig have been active in recent months. In April 2019, Trend Micro spotted an attack campaign leveraging EternalBlue and PowerShell to target systems in Japan with PCASTLE and a Monero coin miner. Several months later, the security firm came across a new family of malware called BlackSquid that used eight notorious exploits to infect vulnerable machines with XMRig.

Protect Your Organization Against Monero-Mining Malware

Security professionals can help defend their organizations against Monero-mining malware like XMRig by disabling JavaScript in web browsers and restricting outbound calls to cryptomining pools as part of a general, concerted effort to defend against cryptocurrency miners. As always, ongoing security awareness training is critical to help the workforce avoid fileless attacks, including campaigns that leverage PowerShell to install malware.

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…