Threat Explorer

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29 June 2015
Risk Impact:
Systems Affected:


PUA.Yontoo.B is a potentially unwanted application that installs a browser extension to display advertisements that appear to be from Facebook.

Note: Virus definitions dated June 26, 2015 or earlier detect this threat as Yontoo.B

Antivirus Protection Dates

  • Initial Rapid Release version 02 October 2014 revision 022
  • Latest Rapid Release version 26 June 2015 revision 008
  • Initial Daily Certified version 25 March 2013 revision 016
  • Latest Daily Certified version 26 June 2015 revision 019
  • Initial Weekly Certified release date 27 March 2013
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.
When the program is executed, it downloads a file from the following remote location:

The file is saved to the following location:

The program then installs extensions for Safari, Google Chrome and Mozilla Firefox to the following locations:
  • $HOME/Library/Safari/Extensions/Yontoo.safariextz
  • $HOME/Library/Application Support/Google/Chrome/Default/Extensions/[CHROME FOLDER NAME]
  • $HOME/Library/Application Support/Firefox/Profiles/[USER PROFILE]/extensions/

Note: Where [CHROME FOLDER NAME] is a folder that is created by Google Chrome.

The program then connects to the following remote locations to download extensions:
  • [http://][REMOVED]
  • [http://][REMOVED]

It may also download updates of itself from the following locations:
  • [https://][REMOVED]
  • [http://][REMOVED]
  • [https://][REMOVED]

The program will then install PageRage, a browser extension that modifies the skin layout of Facebook but also displays advertisements which appear to be from Facebook.
The following instructions pertain to all current and recent Symantec antivirus products for Macintosh.
  1. Update the virus definitions.
  2. Run a full system scan and repair or delete all the files detected.
For specific details on each of these steps, read the following instructions.

1. To update the virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:
  • Running LiveUpdate, which is the easiest way to obtain virus definitions: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the Virus Definitions (LiveUpdate).
  • Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to the Virus Definitions (Intelligent Updater).
The Intelligent Updater virus definitions are available: Read "How to update virus definition files using the Intelligent Updater " for detailed instructions.

2. To scan for and delete the infected files
a. Start your Norton AntiVirus for Macintosh program and make sure that it is configured to scan all the files.
b. Run a full system scan. For more information on how to do this, read the document, "How to install Norton AntiVirus for Macintosh ."
c. If any files are detected, click Repair (if available) or Delete.