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    Archive for March 27th, 2013

    12:03 pm (UTC-7)   |    by

    Our investigation and analysis of last week’s MBR wiper attacks in South Korea is still ongoing. This post summarizes our results and available protection.

    The MBR wiper arrives as a dropper file (detected as TROJ_KILLMBR.SM), which drops four files onto the system:

    • Agentbase.exe –the actual MBR wiper, also detected as TROJ_KILLMBR.SM
    • ~pr1.tmp – a UNIX executable, detected as UNIX_KILLMBR.A
    • Alg.exe – non-malicious file, related to PuTTY client
    • Conime.exe – non-malicious, related to PuTTY client

    However, before it wipes the MBR, it performs two additional routines: firstly, it terminates the processes of two Korean antivirus suites, if these are running on the affected systems. (Other variants we’ve seen also terminate a third antivirus product, which is also Korean.)

    Secondly, it searches for saved SSH credentials from two known SSH clients – mRemote and Secure CRT. It searches the folders where these two clients save credentials, namely:

    • %AppDataLocal%\Felix_Deimel\mRemote\confCons.xml (for mRemote)
    • %Application Data%\VanDyke\Config\Sessions (for Secure CRT)

    It checks the credentials stored at these locations at looks for accounts with root access to servers. If it finds any, the malware will attempt to log onto these servers. It checks the operating system of these servers; if it find any of the following operating systems it will upload the ~pr1.tmp file to this server and run it.

    • AIX
    • HP-UX
    • Linux
    • SunOS

    The actual MBR wiper overwrites the MBR with three repeated strings: PRINCPES, HASTATI. or PR!NCPES. Some variants of this wiper only trigger at or before 2PM on March 20, 2013; others may trigger only at 3PM or later. Deleting the MBR results in the system being unable to boot as normal.

    For newer versions of Windows (Vista and later), some variants of the MBR wiper also deletes all files in all folders on the affected system as well. It restarts the PC, and users are then unable to use their machine.

    Read the rest of this entry »

    Posted in Malware, Targeted Attacks | Comments Off on Summary of March 20 Korea MBR Wiper

    With its rich functionality and accessibility, Evernote is a popular note-taking tool for its many users. Unfortunately, it may also provide the perfect cover for cybercriminals’ tracks.

    We recently uncovered a malware that appears to be using Evernote as a communication and control (C&C) server. Detected as BKDR_VERNOT.A, the malware attempts to connect to Evernote using as its referrer, perhaps to make it look like a malicious user.


    Figure 1. BKDR_VERNOT.A strings showing how it attempts to access Evernote



    Figure 2. BKDR_VERNOT.A connecting to Evernote.


    Figure 3. BKDR_VERNOT.A logging into Evernote.

    The sample we gathered consists of an executable file, which drops a .DLL file and injects it into a legitimate process. The said .DLL file performs the actual backdoor routines.

    Once installed, BKDR_VERNOT.A can perform several backdoor commands such as downloading, executing, and renaming files. It then gathers information from the infected system, including details about its OS, timezone, user name, computer name, registered owner and organization.

    But here’s the interesting part: BKDR_VERNOT.A retrieves its C&C server and queries its backdoor commands in the notes saved in its Evernote account. The backdoor may also use the Evernote account as a drop-off point for its stolen information.

    Unfortunately, during our testing, it was not able to login using the credentials embedded in the malware. This is possibly a security measure imposed by Evernote following its recent hacking issue.

    As stealth is the name of the game, misusing legitimate services like Evernote is the perfect way to hide the bad guys’ tracks and prevent efforts done by the security researchers. Because BKDR_VERNOT.A generates a legitimate network traffic, most antimalware products may not readily detect this behavior as malicious. This can be troubling news not only for ordinary Internet users, but also for organizations with employees using software like Evernote.

    Though this is a clever maneuver to avoid detection, this is not the first time that a legitimate service like Evernote was used as a method of evasion. Late last year, BKDR_MAKADOCS.JG was found using Google Docs to communicate to its C&C server. Similarly, the file-hosting site Sendspace was used as a storage of stolen information by TSPY_SPCESEND.A, a spyware that gathers MS Word and Excel files. Malware like BKDR_MAKADOCS.JG, TSPY_SPCESEND and now BKDR_VERNOT.A only show the extent that online bad guys will go to to hide their schemes.

    To avoid this threat, you must always be cautious with visiting unknown websites and opening email messages. Trend Micro Smart Protection Network detects both the malware cited in this blog entry.

    Update as of April 4, 2013 1:00 AM PDT

    We have been in communication with Evernote regarding this incident, and are working with them to detect any other malware that may attempt to use Evernote for malicious purposes.

    We also wish to reiterate that BKDR_VERNOT.A was unable to actually log into Evernote because of the incorrect credentials that were hard-coded into the malware. No notes or other information on Evernote servers was actually read, created, or modified.

    Had the malware been successful in accessing the notes, it would have used the Evernote account to:

    • Retrieve information about C&C server in one of the notes saved
    • Obtain backdoor commands from the notes saved
    • Use the Evernote account as a drop-off point for stolen information

    After getting commands from the Evernote account, the malware would have been able to execute the following backdoor commands:

    • Download files
    • Execute files
    • Rename files
    • Unzip archive files
    Posted in Malware | 1 TrackBack »


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