1. Symantec/
  2. Security Response/
  3. Trojan.Pidief


Risk Level 2: Low

December 17, 2009
May 8, 2014 2:28:58 PM
Infection Length:
Systems Affected:
CVE References:
CVE-2007-5020, CVE-2007-5659, CVE-2007-5663, CVE-2007-5666, CVE-2008-0655, CVE-2008-0667, CVE-2008-0726, CVE-2008-2042, CVE-2008-2992, CVE-2009-0658, CVE-2009-0927, CVE-2009-4324, CVE-2010-0188, CVE-2010-1297, CVE-2013-0640, CVE-2013-0641, CVE-2014-5256
1. Prevention and avoidance
1.1 User behavior and precautions
1.2 Patch operating system and software
1.3 Address blocking
1.4 Disable JavaScript in Adobe Reader and Acrobat
1.5 Disable the display of PDF documents in the Web browser
2. Infection method
2.1 Spam email
2.2 Targeted attacks
2.3 Websites and exploit packs
3. Functionality
3.1 System modifications
3.2 Network activity
4. Additional information

The following actions can be taken to avoid or minimize the risk from this threat.

1.1 User behavior and precautions
Users should be aware that email messages with malicious content may appear to have been sent by people known to them, and as such the fact that the sender is known does not guarantee the safety of any particular message. Users should avoid opening email attachments unless their authenticity can be verified.

Spam emails may contain malicious links that have been disguised or otherwise made to appear benign. Users should exercise caution when following links in email messages, especially if:
  • The sender is not known, or
  • Given the sender, the characteristics of the email are unusual, or
  • The link is to an unknown domain or an executable file

Users should use caution when clicking links in such emails. Basic checks such as hovering with the mouse pointer over each link will normally show where the link leads to. For example, users can check an online website rating services such as safeweb.norton.com to see if the site is deemed safe to visit.

1.2 Patch operating system and software
Users are advised to ensure that their operating systems and any installed software are fully patched, and antivirus and firewall software are up to date and operational. Users are recommended to turn on automatic updates if available so that their computers can receive the latest patches and updates when they are made available.

This threat is known to be spread by exploiting certain vulnerabilities. Installation of the following patches will reduce the risk to your computer.

1.3 Address blocking
Block access to the following addresses using a firewall, router, or add entries to the local hosts files to redirect the following addresses to
  • adxdnet.net
  • adxdnet.net
  • aop1.homelinux.com
  • connectproxy.3322.org
  • csport.2288.org
  • epochtimes.3322.org
  • fc.webmasterpro.de
  • foruminspace.com
  • google-analytics.dynalias.org
  • hession0345.dnsrd.com
  • infonews.ath.cx
  • js001.3322.org
  • microsoft.acmetoy.com
  • microsoft.instanthq.com
  • microsoft.proxydns.com
  • newsplaza.net
  • ssa.adxdnet.net

Note: This is not an exhaustive list as the threat contact other locations.

1.4 Disable JavaScript in Adobe Reader and Acrobat
Many of the vulnerabilities associated with the Adobe products use JavaScript to execute the malicious code. By disabling JavaScript in these products, it may prevent some exploits from executing. JavaScript can be disabled using the Preferences menu.
  1. Click Edit > Preferences.
  2. Select JavaScript in the pane on the left-hand side.
  3. Uncheck Enable Acrobat JavaScript.

1.5 Disable the display of PDF documents in the Web browser
Furthermore, this type of Trojan utilizes vulnerabilities that are triggered through the use of Web browser plugins to display the PDF document. Preventing PDF documents from opening inside a Web browser will help prevent some exploits from executing.

To prevent PDF documents from automatically being opened in a Web browser, perform the following actions:
  1. Click Edit > Preferences.
  2. Select Internet in the pane on the left-hand side.
  3. Uncheck Display PDF in browser.

This threat is known to infect computers through a number of methods. Each of these methods is examined in more detail below.

2.1 Spam email
Spam email is one of the primary infection methods used to propagate this threat. The volume of spam emails can be high and the contents are frequently changed and updated. While some emails include a PDF attachment, it is also common for the email to contain a link to a PDF document also.

The topic of the spam email can vary depending on the attack. The topic may often follow a recent news item or scandal or, in the case of targeted attacks, a topic of interest to an individual within an organization. The following are some example email details that have been used by this threat.

  • IRS e-file refund notification
  • Important Information - U.S. Treasury Department **
  • The settings for the [EMAIL NAME]@[DOMAIN NAME] were changed
  • Royal Mail Delivery Invoice #[RANDOM NUMBER]
  • INVOICE - alacrity
  • INVOICE - depredate
  • US Soldiers Killed in Action Since Obama's Inauguration

  • After the last annual calculations of your fiscal activity we have determined that you are eligible to receive [AMOUNT]$ tax refund under section 501(c) (18) of the Internal Revenue Code. Please submit the Tax Refund Request Form and allow us 3-9 days to process it.

    Yours faithfully,
    [NAME], Commissioner

    This notification has been sent by the Internal Revenue Service, a bureau of the Department of the Treasury.

  • We missed you, when trying to deliver.
    Please view the invoice and contact us with any questions.
    We will try to deliver again the following business day.

Attachment file names
  • Happy Halloween.pdf
  • 1.pdf
  • Elvis_Presley_is_alive!!!.pdf

Known topics used
The following are topics that Symantec have observed in use in spam emails propagating this threat family. This is not an exhaustive list, however, as the topics in the spam emails may vary depending on the attack. Spam email may also often make use of recent news events or current popular topics.
  • Tax refunds
  • Postal delivery failures
  • Security upgrade to mailing service

2.2 Targeted attacks
In recent times, targeted attacks against private and government organizations have become more common. These types of attacks, known as Advanced Persistent Threats (APT), typically begin with an email that is sent to an individual, or small group of individuals, within an organization. The email is designed to look legitimate. In other words, the email appears as though it has been sent by somebody the recipient trusts and the subject matter will often be related to the recipient's area of business. This can be done by researching publicly available information about the company and its employees, such as from the company or social networking websites.

In order to install the malware, the user must be tricked into either clicking a malicious link or launching a malicious attachment. In the more sophisticated attacks, the attacker will use a new zero day vulnerability, as this will have a greater success rate.

In July 2009, we observed an almost textbook execution of a targeted attack in the form of the Trojan.Hydraq incident (a.k.a., Aurora). In this attack a PDF file was used to exploit the Adobe Acrobat, Reader, and Flash Player Remote Code Execution Vulnerability (BID 35759). This PDF file installed a Trojan horse which was an earlier version of the current Trojan.Hydraq.

Usually, when this type of attack is performed against individuals or by less sophisticated attackers, the attack is used to gather all the information immediately available and move on to the next target. However, APT attacks are designed to remain undetected in order to gather information over prolonged periods.

According to the Symantec Global Internet Security Threat Report Trends for 2009 Volume XV, while attacks using PDF vulnerabilities accounted for only 11% of attacks in 2008, that number increased to 49% in 2009. It is obvious, therefore, that attackers are utilizing the vulnerabilities in this popular software in order to perform more malicious actions throughout the computing world.

2.3 Websites and exploit packs
This threat has also been known to be hosted on websites that causes a user to unknowingly download the threat on to their computer.

Furthermore, some attackers are utilizing exploit packs, e.g. the Eleonore and Nuke exploit packs. When a user visits one of these websites, the exploit packs typically probe the client computer by sending multiple exploits down to it. If any of the exploits are successful, then the next stage of the attack commences. This typically involves the downloading or installing of further malware, which is done behind the scenes.


Once the PDF document has been opened, and the exploit has successfully run, the Trojan can begin executing its malicious payload. The most common functionality that this particular Trojan has been observed performing is dropping and downloading other malware on to the computer. This Trojan, therefore, can be considered as a staging point for further attacks. The following list of malware has already been linked with this particular threat:

The following side effects may be observed on computers compromised by members of the threat family.

Files created
The Trojan may drop and execute some of the following files:
  • %CurrentFolder%\ldr.exe (Downloader)
  • %CurrentFolder%\tong.exe
  • %Temp%\xpre.exe
  • %Temp%\prun.exe
  • %Temp%\wavvsnet.exe
  • %Temp%\snapsnet.exe
  • %Temp%\rasesnet.exe
  • %Temp%\searsnet.exe
  • %Temp%\incasnet.exe
  • %Temp%\winvsnet.exe
  • %Temp%\SVCHOST.EXE (Backdoor.Trojan)
  • %Temp%\TEMP.EXE (Backdoor.Trojan)
  • %System%\[EIGHT RANDOM CHARACTERS].DLL (Backdoor.Trojan)
  • %SystemDrive%\a.exe
  • %SystemDrive%\a.pdf
  • %System%\chkzero.exe
  • %Temp%\filepages.sys
  • %Temp%\temp.sys
  • %Temp%\temp.txt
  • C:\Documents and Settings\All Users\Application Data\SVCH0ST.dll
  • C:\Documents and Settings\All Users\Application Data\svchost.exe
  • %Temp%\SUCHOST.EXE (Trojan Horse)
  • %Temp%\TEMP.EXE
  • %Temp%\AdobeUpdate.exe
  • %UserProfile%\Application Data\AcroRd32.exe
  • %Temp%\upt.exe (Backdoor.Trojan)
  • %Windir%\EventSystem.dll (Backdoor.Trojan)
  • %System%\qmgr.dll (Backdoor.Trojan)
  • %System%\dllcache\qmgr.dll (Backdoor.Trojan)
  • %System%\es.ini

Files/folders deleted

Files/folders modified

Registry subkeys/entries created
The Trojan may create the following registry entries:
  • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\"RUN_XY_Zer0" = "a.exe"
  • HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\Marks Info\"Mark" = "kkk"
  • HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\Marks Info\"SystemTime" = "2009-5-21-20"

It may also create the following registry subkeys:
  • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RUN_XY_Zer0
  • HKEY_CURRENT_USER\Software\Microsoft\Windows\Marks Info
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\rewqrew
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DETrueTime

Registry subkeys/entries deleted

Registry subkeys/entries modified (final values given)

The threat may perform the following network activities.

Typically, the main purpose of this particular threat is to drop or download more malware on to the compromised computer. When the user opens the malicious PDF document, the threat may download more malware on to the computer from some of the following locations:
  • (Downloader)
  •[REMOVED] (Trojan.Zonebac)
  • adxdnet.net/code/srun[REMOVED]
  • epochtimes.3322.org/update.ex[REMOVED] (Downloader)
  • fc.webmasterpro.de/as_nosc[REMOVED]
  • foruminspace.com/documents/dprk/ab.[REMOVED] (Infostealer)
  • microsoft.acmetoy.com
  • microsoft.instanthq.com
  • microsoft.proxydns.com
  • newsplaza.net/nice/winver[REMOVED] (Trojan.Dropper)
  • ssa.adxdnet.net/get[REMOVED][RANDOM CHARACTERS]

Note: This is not an exhaustive list and the threat may download malware from other locations.

Other network activity
Furthermore, members of the threat family have also been seen to directly upload information from the compromised computer. For example, some of the threats may perform the following actions:

  • Contact js001.3322.org in order to send information from the compromised computer.
  • Connect to google-analytics.dynalias.org/ddr/ddrh[REMOVED] to upload or download information from the compromised computer.
  • Open a back door that connects to hession0345.dnsrd.com on TCP port 443.
  • Open a back door that connects to aop1.homelinux.com
  • Open a back door that connects to connectproxy.3322.org
  • Open a back door that connects to csport.2288.org

For more information relating to this threat family, please see the following resources:


Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.
Writeup By: Éamonn Young and Hon Lau
Summary| Technical Details| Removal

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