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Discovered: December 17, 2009
Updated: May 08, 2014 2:28:58 PM
Type: Trojan
Infection Length: Varies
Systems Affected: Windows
CVE References: CVE-2010-0188 | CVE-2014-5256 | CVE-2008-0726 | CVE-2013-0641 | CVE-2008-0655 | CVE-2013-0640 | CVE-2007-5659 | CVE-2008-2992 | CVE-2009-0927 | CVE-2009-4324 | CVE-2007-5020 | CVE-2007-5666 | CVE-2008-2042 | CVE-2010-1297 | CVE-2007-5663 | CVE-2008-0667 | CVE-2009-0658

Trojan.Pidief is a detection for a family of Trojans that exploit one or more Adobe Reader and Acrobat Vulnerabilities in order to drop or download additional malware on to the compromised computer.


Typically an attacker would entice a user to click on a malicious link or send a malicious PDF by email. Email has proven to be an efficient technique that has allowed this Trojan to reach large numbers of computers in a short space of time. The content of the spam emails constantly varies, so users should always be vigilant about any PDF documents that they receive by email.

The Trojan may also arrive on a computer as a result of websites that contain exploit packs. These websites contain functionality that may allow a remote attacker to identify which vulnerabilities exist on a certain computer. Once the vulnerability has been identified, the attacker can exploit it to perform further malicious activities on the compromised computer.

Malicious PDF files are often used in targeted attacks on individual or select groups within organizations. The aim of such attacks vary but may involve collection and theft of sensitive and proprietary information. In these attacks, the threats operate in a stealthy manner, trying to remain undetected for as long as possible in order to maximize the amount of information that can be stolen.

The malicious PDF file typically contains an exploit. When the file is opened, the exploited code runs and then other files are dropped and executed. Alternatively, files may also be downloaded and installed. This threat family is known to be associated with dropping or downloading other threats such as Backdoor.Trojan and Infostealer .


Symantec has observed the following geographic distribution of this threat.

Symantec has observed the following infection levels of this threat worldwide.

The following content is provided by Symantec to protect against this threat family.

Antivirus signatures

Antivirus (heuristic/generic)

Browser protection
Symantec Browser Protection is known to be effective at preventing some infection attempts made through the Web browser.

Intrusion Prevention System

Symantec Endpoint Protection – Application and Device Control
Symantec Security Response has developed an Application and Device Control (ADC) Policy for Symantec Endpoint Protection to protect against the activities associated with this threat. ADC policies are useful in reducing the risk of a threat infecting a computer, the unintentional removal of data, and to restrict the programs that are run on a computer.

This particular ADC policy can be used to help combat an outbreak of this threat by slowing down or eliminating its ability to spread from one computer to another. If you are experiencing an outbreak of this threat in your network, please download the policy .

To use the policy, import the .dat file into your Symantec Endpoint Protection Manager. When distributing it to client computers, we recommend using it in Test (log only) mode initially in order to determine the possible impacts of the policy on normal network/computer usage. After observing the policy for a period of time, and determining the possible consequences of enabling it in your environment, deploy the policy in Production mode to enable active protection.

For more information on ADC and how to manage and deploy them throughout your organization, please refer to the Symantec Endpoint Protection Administration Manual (PDF).

Note: The ADC policies developed by Security Response are recommended for use in outbreak situations. While useful in such situations, due to their restrictive nature they may cause disruptions to normal business activities.

Antivirus Protection Dates

  • Initial Rapid Release version December 17, 2009 revision 001
  • Latest Rapid Release version September 09, 2019 revision 023
  • Initial Daily Certified version December 17, 2009 revision 005
  • Latest Daily Certified version August 15, 2019 revision 002
  • Initial Weekly Certified release date December 23, 2009

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Technical Description

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 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

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)
  •[REMOVED] (Downloader)
  •[REMOVED] (Infostealer)
  •[REMOVED] (Trojan.Dropper)

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 in order to send information from the compromised computer.
  • Connect to[REMOVED] to upload or download information from the compromised computer.
  • Open a back door that connects to on TCP port 443.
  • Open a back door that connects to
  • Open a back door that connects to
  • Open a back door that connects to

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.


You may have arrived at this page either because you have been alerted by your Symantec product about this risk, or you are concerned that your computer has been affected by this risk.

Before proceeding further we recommend that you run a full system scan . If that does not resolve the problem you can try one of the options available below.

If you are a Norton product user, we recommend you try the following resources to remove this risk.

Removal Tool

If you have an infected Windows system file, you may need to replace them using from the Windows installation CD .

How to reduce the risk of infection
The following resources provide further information and best practices to help reduce the risk of infection.

If you are a Symantec business product user, we recommend you try the following resources to remove this risk.

Identifying and submitting suspect files
Submitting suspicious files to Symantec allows us to ensure that our protection capabilities keep up with the ever-changing threat landscape. Submitted files are analyzed by Symantec Security Response and, where necessary, updated definitions are immediately distributed through LiveUpdate™ to all Symantec end points. This ensures that other computers nearby are protected from attack. The following resources may help in identifying suspicious files for submission to Symantec.

Removal Tool

If you have an infected Windows system file, you may need to replace them using from the Windows installation CD .

How to reduce the risk of infection
The following resource provides further information and best practices to help reduce the risk of infection.
Protecting your business network

The following instructions pertain to all current Symantec antivirus products.

1. Performing a full system scan
How to run a full system scan using your Symantec product

2. Restoring settings in the registry
Many risks make modifications to the registry, which could impact the functionality or performance of the compromised computer. While many of these modifications can be restored through various Windows components, it may be necessary to edit the registry. See in the Technical Details of this writeup for information about which registry keys were created or modified. Delete registry subkeys and entries created by the risk and return all modified registry entries to their previous values.

Writeup By: Éamonn Young and Hon Lau