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Don't Feel Left Out: Ransomware for IT Security Enthusiasts!

Secure List feed for B2B - Tue, 04/07/2015 - 05:45

Macros are so hot right now

It's getting dark outside and our favorite mail client beeps with excitement for a new missive in our inbox, something interesting perhaps? A rapid glimpse at the contents of the message should indicate that a malicious campaign will play the starring role in what follows. An included attachment reveals itself as a malicious document with password-protected embedded macros. Moreover, a quick analysis of the file shows that it's dropping an executable payload to the system, which further piques our interest in this devious sample:

After opening the file, and only once the victim has been lured into enabling macros,  a seemingly innocuous Word document is shown.

File metadata betrays the developer's rush in crafting this file, using the Russian language letters "фыв" to fill the tags section:

"фыв" corresponds to the "asd" letter combination on Latin keyboards so often used as mindless filler.

Delving into the code

The second stage malicious script containing the instructions is downloaded from a public entry hosted on Pastebin in base64 encoding mode.

The full instruction set is 101 lines long and at the time of writing it counts with more than 5k reads. So this seems like a reliable indicator of the number of potential infections by this malware.

It is important to mention that upon discovery of the initial malicious document, Virustotal showed a null detection rate (however, the executable payload itself was detected by Kaspersky as Trojan-Ransom.Win32.Foreign.mdst)

The decoded script looks like this:

The decoded base64 payload downloaded from Pastebin fetches a file that includes several tokens to be used by the beckoning VBS script. Each token represents a section of the code that needs to be called in a specific order to achieve infection. The sections are named using a generic convention such as 'text20', 'text21', 'stext1', etc. Using the 'Tort' function implemented in the VBS script module, the instructions are deobfuscated and then outputted for execution.

The payload Trojan-Ransom.Win32.Foreign.mdst connects to an onion-based domain via the Tor2Web service

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In the case of the ' ' section, we can find a PowerShell script being called using the '-noexit' option, which according to Microsoft's Technet documentation is commonly used when running scripts via the command prompt (cmd.exe) so as to avoid exiting after execution. It's worth mentioning the second parameter, which sets the execution policy to bypass mode. Interestingly, by using a simple command line option this malicious creation is able to bypass the PowerShell execution policy configured in the system.

The file set for execution by PowerShell is also set by the original VBS script. A simple yet annoying obfuscation is in charge of getting the final string to be passed as a parameter.

As per the instructions above, the 'currentFile' variable will be replaced by the value of Chr(34) or a quotation mark, and the value of the variables PH2, FL2 and another static text value. Both PH2 and FL2 variables are set at the beginning of the execution of the script, FL2 being the random text used to name several files inside a temporary location set by PH2.

Even though the mechanism is not very complex, we can see that the malware writers took any measures available to slow down analysis and hide the real purpose of their code, even if by virtue of being a script it should be human readable.

We already reported the abusive Pastebin URL.

Payload

The payload is a binary PE file (self-extracting archive or SFX) named "file.exe". Upon execution, "file.exe" is copied to "C:\Windows\System32\WinSrv32.exe" and deleted from its original calling location. Persistence in the infected system is obtained via a registry key written in the following branch "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run".

This payload connects to an onion-based domain via the Tor2Web service.

The mention of a hostname refers to the front-facing side of the um6fsdil5ecma5kf.onion domain that serves as a C2 of the payload malware.

Detection names for malware 239d4f67692a5883574e3c496d88979c logmein_coupon.doc Trojan-Downloader.MsWord.Agent.hz 41d605b3981f330bd893b2dfd6e1d890 file.exe Trojan-Ransom.Win32.Foreign.mdst

Post-Cryptanalysis, TrueCrypt Alternatives Step Forward

Threatpost for B2B - Mon, 04/06/2015 - 14:11
CipherShed and VeraCrypt developers stand ready to step in for TrueCrypt now that the cryptanalysis phase of the audit is complete and no backdoors were discovered.

Linux Australia Hit With Server Breach

Threatpost for B2B - Mon, 04/06/2015 - 12:14
Linux Australia, a consortium in charge of organizing Linux conferences across the continent, acknowledged over the weekend it was breached by attackers last month.

Snapchat Publishes First Transparency Report

Threatpost for B2B - Mon, 04/06/2015 - 10:58
Snapchat has released its first transparency report, covering a four-month period from November through February, and the data shows that the company didn’t receive any National Security Letters and got fewer than 400 total requests for data from the United States government. Snapchat, a California company that runs a popular chat and media-sharing service, said in the report […]

SWF Files Injecting Malicious iFrames on WordPress, Joomla Sites

Threatpost for B2B - Fri, 04/03/2015 - 12:36
Researchers have seen an uptick in Adobe Flash .SWF files being used to trigger malicious iFrames across websites.

VMware Fixes Java Information Disclosure Vulnerability

Threatpost for B2B - Fri, 04/03/2015 - 11:03
VMware has issued an update to a number of its products fixing an information disclosure bug in Oracle's Java runtime environment.

Dyre Banking Malware A Million-Dollar Threat

Threatpost for B2B - Fri, 04/03/2015 - 10:12
IBM warns banks and corporate officers of a change to the dangerous Dyre banking Trojan that involves the phone scam used to bypass fraud detection, and a DDoS attack that distracts security teams away from big-money transfers.

Threatpost News Wrap, April 2, 2015

Threatpost for B2B - Fri, 04/03/2015 - 09:00
Dennis Fisher and Mike Mimoso talk about Google's decision to drop Chinese CA CNNIC from Chrome's trust store, the scope of the malvertising threat and Verizon's super cookie use.

Audit Concludes No Backdoors in TrueCrypt

Threatpost for B2B - Thu, 04/02/2015 - 13:50
Auditors performing a cryptanalysis of TrueCrypt found four vulnerabilities, but zero backdoors in the popular open source encryption software.

Google Report Lauds Android Security Enhancements

Threatpost for B2B - Thu, 04/02/2015 - 13:22
Google's first Android Security Report puts some hard data behind the effectiveness of the security enhancements it has put into the OS.

Google Awards $5k Bounty for YouTube Video Delete Bug

Threatpost for B2B - Thu, 04/02/2015 - 11:23
A Russian security researcher discovered that he could delete any video on YouTube by sending a simple POST request in YouTube's Creator Studio.

Google, Mozilla Drop Trust in Chinese Certificate Authority CNNIC

Threatpost for B2B - Thu, 04/02/2015 - 07:59
UPDATE–Google has taken the unusual step of completely removing trust from Chrome for the Chinese certificate authority CNNIC in the wake of an incident in which certificates issued by the CA were misused. Mozilla followed suit on Thursday, also removing CNNIC from its trust store. Google officials announced the severe decision on Wednesday, saying that […]

Little Change in Online Behavior Following Snowden Revelations

Threatpost for B2B - Wed, 04/01/2015 - 15:15
Pew Research Center survey finds that most Americans have done little or nothing to change their online behaviors nearly two years after the first NSA spying revelations emerged.

Students Build Open Source Web-Based Threat Modeling Tool

Threatpost for B2B - Wed, 04/01/2015 - 15:00
Students at St. Mary's University in Canada released to open source a web-based threat modeling tool called Seasponge that they hope will provide an alternative to Microsoft's free tool.

Critical Vulnerabilities Affect JSON Web Token Libraries

Threatpost for B2B - Wed, 04/01/2015 - 14:58
Critical vulnerabilities exist in several JSON Web Token (JWT) libraries – namely the JavaScript and PHP versions – that could let an attacker bypass the verification step.

Verizon Allows Opt Out of UIDH Mobile Supercookie

Threatpost for B2B - Wed, 04/01/2015 - 13:30
Verizon Wireless has made a change that now allows customers to opt out of the ad-targeting program that relies on the so-called supercookie identifier that was inserted into Web requests users send. The use of the identifier, known as a UIDH, drew the ire of privacy advocates and users when it was exposed last year. […]
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