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The Cofense Phishing Defense CenterTM  has detected a new wave of attacks targeting the US taxpayer by delivering Amadey botnet via phishing emails. Amadey is a relatively new botnet, first noted late in Q1 of 2019. Known for its simplicity, it is available to hire for a very steep price compared to other commercially available botnets with similar functionality. Threat groups like TA505 have been known to leverage Amadey botnet as recently as July 2019 to deliver secondary malware like FlawedAmmy (RAT) and email stealers.

Here’s how a typical attack works:

Figure 1: Infection chain

Figure 2: Email Body

The email body reports to be from the Internal Revenue Service (IRS) and claims that the recipient is eligible for a tax refund. The recipient is presented with a “one time username and password” and urged to click the “Login Right Here” button. As seen above in figure 1, the login button is an embedded Hyperlink and redirects to hxxp://yosemitemanagement[.]com/fonts/page5/. Here the recipient is presented with an IRS login page to enter the one-time password.

Figure 3: Infection Page 

Once the recipient is logged into the fake IRS portal they are informed that they have “1 pending refund” and asked to download a document, print and sign, then either mail it back or upload a copy to the portal. When the recipient clicks to download the document, a zip file called “document.zip” is presented, which contains a Visual Basic script dropper.

Fig 4. Obfuscated vbs Script

The VBScript is highly obfuscated and encrypted. For more details on how this VBScript was decoded, please take a look at the Cofense™ Labs detailed write-up, which can be found here.

At a high level, once executed the script decrypts itself at run time and drops an executable file called “ZjOexiPr.exe” in C:\Users\Byte\AppData\Local\Temp\. Once dropped it then proceeds to install the executable kntd.exe in C:\ProgramData\0fa42aa593 and execute the process.

Figure 5: Persistence 

The Amadey process installs itself in C:\ProgramData\0fa42aa593 and to maintain persistence it uses Reg.exe, a command line tool for editing the registry. Next the script issues the command “REG ADD “HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders” /f /v Startup /t REG_SZ /d C:\ProgramData\0fa42aa593”

Figure 6: C2 channels

Amadey instantly beacons out to its command and control (C2) channels sending system diagnostic information back to the C2 server and awaits further instructions. Amadey connects out via HTTP on port 80 to multiple C2 servers.

Figure 7: Network Traffic

If we take a closer look at the HTTP traffic we can see that Amadey sends system information back to its C2 server.

From the values given we can infer that:

ID – Unique identifier of the infected system

VS – Version of Amadey

OS – Operating system

AV – Antivirus

PC – System name

UN – Username

Additional Analysis:

Cofense Labs takes this analysis a bit deeper to deobfuscate the malware. To learn more, check out the Lab Notes on this analysis: https://cofenselabs.com/i-see-what-you-did-there/

Indicators of Compromise (IOCs):

Malware Artifacts

File  MD5 Hash Value
document.zip 7f9a3244d23baed3b67416e32eb949bd
a4-155QFYXY.vbs 79d24672fff4c771830b4c53a7079afe
kntd.exe a046030e2171ddf787f06a92941d37ca

 Network Connections

URL  IP
hxxp://yosemitemanagement[.]com/fonts/page5/ 160[.]153[.]138[.]163
hxxp://ledehaptal[.]ru/f5lkB/index[.]php 78[.]40[.]109[.]187
hxxp://nofawacat[.]com/f5lkB/index[.]php 179[.]43[.]139[.]222
hxxp://Ip[.]hoster[.]kz 192[.]4[.]58[.]78

 

HOW COFENSE CAN HELP

Cofense Resources

Cofense PhishMeTM offers a phishing simulation, “Tax Refund Notice –Amadey Botnet,” to educate users on the attack described in today’s blog.

89% of phishing threats delivering malware payloads analysed by the Cofense Phishing Defense Center bypassed secure email gateways. Condition users to be resilient to evolving phishing attacks with Cofense PhishMe.

Remove the blind spot with Cofense ReporterTM—give users a one-click tool to report suspicious messages, alerting security teams to potential threats.

Quickly turn user reported emails into actionable intelligence with Cofense TriageTM. Reduce exposure time by rapidly quarantining threats with Cofense VisionTM.

Easily consume phishing-specific threat intelligence to proactively defend your organisation against evolving threats with Cofense IntelligenceTM.

Thanks to our unique perspective, no one knows more about REAL phishing threats than Cofense. To understand current threats, read the 2019 Phishing Threat & Malware Review.

 

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