BlackBerry is warning of a widespread campaign targeting online payment businesses with web skimmers for more than a year.
Dubbed Silent Skimmer, the campaign initially focused on organizations in the APAC region, but has been targeting businesses in Canada and the United States as well since October 2022, and appears to be expanding to new areas.
Likely of Chinese origin, the threat actor behind the campaign appears to be experienced and resourceful, adjusting its infrastructure as it expands to new territories, to avoid detection.
The attackers have been observed targeting multiple industries that host or create payment infrastructure, including online businesses and point-of-sales (PoS) providers, exploiting internet-facing applications for initial access, and deploying various tools to escalate privileges, execute code, and gain remote access.
All tools and post-exploitation payloads are hosted on an attacker-controlled HTTP File Server (HFS) deployed on a temporary virtual private server (VPS). The VPS location appears to be chosen based on the victim’s location, BlackBerry explains.
The threat actor exploits a .NET deserialization vulnerability (CVE-2019-18935) in the Progress Telerik UI for ASP.NET AJAX to execute code remotely on targeted servers. The payload attempts to execute code from a remote location, to deploy a remote access tool (RAT) in the form of a PowerShell script.
The RAT allows the attackers to gather system information, download or upload files, search for files, connect to a database, and more.
Analysis of the server the RAT connects to revealed a broad range of tools, including downloader scripts, remote access scripts, webshells, exploits, and Cobalt Strike beacons. On the server, BlackBerry also discovered Fast Reverse Proxy (RFP), a tool that allows attackers to expose local servers located behind a NAT.
The purpose of the campaign, however, is to deploy a web skimmer on the payment checkout pages of the targeted victim organizations, to harvest user information such as billing information and credit card details. The data is exfiltrated using Cloudflare.
The threat actor, BlackBerry says, mainly targets regional websites that collect payment data, and the attacks appear opportunistic, rather than industry-specific.
“The threat actor or group behind this campaign remains unknown at the time of writing. However, given that the GitHub repository they used is associated with Chinese-speaking developers, the code In PowerShell RAT is in simplified Chinese language, and the attacker’s [command-and-control server] is located in Asia (specifically Japan), it’s likely the threat actor speaks the Chinese language and lives or operates in Asia,” BlackBerry says.