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Discovered: June 20, 2008
Updated: June 24, 2008 11:53:44 PM
Also Known As: BKDR_HOVDY.A [Trend]
Type: Trojan
Infection Length: 57,747 bytes
Systems Affected: Mac

AplS.Saprilt.A is a Trojan horse that lowers security settings and opens a back door on the compromised computer.

Antivirus Protection Dates

  • Initial Rapid Release version June 20, 2008 revision 021
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version June 20, 2008 revision 025
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date June 25, 2008

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

Technical Description

When the Trojan is executed, it creates the following folders:

  • /Library/WebServer/Documents/.PS_Store
  • ~/Sites/images/.PS_STORE/

It then creates the following files:
  • /Users/Shared/SC Info/.candidates
  • /Users/Shared/SC Info/.accounts
  • /Users/Shared/SC Info/.hashes
  • ~/Public/.howdy
  • /Users/Shared/.howdy
  • /Library/WebServer/Documents/.howdy

It installs a back door on the computer, which may allow a remote attacker to perform the following actions:
  • Attempt to add the user named "USER" with a blank password to the /etc/sudoers folder using the following vulnerability:
    Apple Mac OS X AppleScript ARDAgent Shell Local Privilege Escalation Vulnerability (BID 29831)
  • Attempt to add the user "nobodyd" with password "a secret" on the computer
  • Attempt to modify the Apache httpd.conf file, in order to load the PHP library, and then activate the Apache Webserver
  • Install a shell that attempts to connect back to the attacker every hour by using crontab
  • Attempt to connect back to the attacker through a VNC connection every hour by using crontab
  • Install a PHP shell inside /Library/WebServer/Documents/.PS_STORE/ or ~/Sites/images/.PS_STORE/

The Trojan then attempts to exploit the following vulnerability, if it fails to get root privileges on the compromised computer:
Apple Mac OS X Pre 10.4.8 Multiple Security Vulnerabilities (BID 20271 )

NOTE: This vulnerability affects OS X 10.4 through 10.4.7.

Next, it may create the following files:
  • /Library/Caches/AStht_v06.app/Contents
  • /Library/Caches/AStht_v06.app/Contents/Info.plist
  • /Library/Caches/AStht_v06.app/Contents/MacOS
  • /Library/Caches/AStht_v06.app/Contents/MacOS/applet
  • /Library/Caches/AStht_v06.app/Contents/PkgInfo
  • /Library/Caches/AStht_v06.app/Contents/Resources
  • /Library/Caches/AStht_v06.app/Contents/Resources/._logKext.pkg
  • /Library/Caches/AStht_v06.app/Contents/Resources/._phpshell-2.1
  • /Library/Caches/AStht_v06.app/Contents/Resources/._Vine Server.app
  • /Library/Caches/AStht_v06.app/Contents/Resources/applet.icns
  • /Library/Caches/AStht_v06.app/Contents/Resources/applet.rsrc
  • /Library/Caches/AStht_v06.app/Contents/Resources/com.AStht.config.plist
  • /Library/Caches/AStht_v06.app/Contents/Resources/description.rtfd
  • /Library/Caches/AStht_v06.app/Contents/Resources/description.rtfd/TXT.rtf
  • /Library/Caches/AStht_v06.app/Contents/Resources/MachEx
  • /Library/Caches/AStht_v06.app/Contents/Resources/Scripts/main.scpt

It then drops files relating to the following applications on to the computer:
  • logKext
  • Vine Server
  • phpshell-2.1
  • isightcapture

Then it adds itself to the following folder, so that it executes every time the compromised computer starts:

It also attempts to add itself to the list of items that open at login:

Next, the Trojan disables the scheduled update that checks for the current user by modifying Software Update.

Next, the Trojan modifies Software Update in order to disable automatic scheduled updates.

It then lowers security settings by attempting to stop antivirus software from getting updates.

The Trojan attempts to bruteforce the following information from local system accounts:
  • User names and their associated passwords
  • Openfirmware passwords
  • Keychain autologin passwords
  • Ad-hoc wifi network passwords
  • Apple Remote Desktop passwords

It then stores the above information and attempts to send it back to the attacker using a Web mail service.

The Trojan can also create a symbolic link to a fake sudo command named .sudo2 in order to steal user passwords during authentication.


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.


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.

Writeup By: Alfredo Pesoli