AplS.Saprilt.B

Discovered:

June 20, 2008

Updated:

June 24, 2008 4:08:16 PM

Type:

Trojan

Infection Length:

62,944 bytes

CVE References:

CVE-2006-4387, CVE-2006-4390, CVE-2006-4391, CVE-2006-4392, CVE-2006-4393, CVE-2006-4394, CVE-2006-4395, CVE-2006-4397, CVE-2006-4399, CVE-2008-2830

Once executed, the Trojan 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
• /Library/WebServer/Documents/.PS_STORE/AUTHORS
• /Library/WebServer/Documents/.PS_STORE/ChangeLog
• /Library/WebServer/Documents/.PS_STORE/SECURITY
• /Library/WebServer/Documents/.PS_STORE/COPYING
• /Library/WebServer/Documents/.PS_STORE/INSTALL
• /Library/WebServer/Documents/.PS_STORE/phpshell.php
• /Library/WebServer/Documents/.PS_STORE/pwhash.php
• /Library/WebServer/Documents/.PS_STORE/README
• /Library/WebServer/Documents/.PS_STORE/style.css
• /Library/WebServer/Documents/.PS_STORE/config.php
• ~/Sites/images/.PS_STORE/AUTHORS
• ~/Sites/images/.PS_STORE/ChangeLog
• ~/Sites/images/.PS_STORE/SECURITY
• ~/Sites/images/.PS_STORE/COPYING
• ~/Sites/images/.PS_STORE/INSTALL
• ~/Sites/images/.PS_STORE/phpshell.php
• ~/Sites/images/.PS_STORE/pwhash.php
• ~/Sites/images/.PS_STORE/README
• ~/Sites/images/.PS_STORE/style.css
• ~/Sites/images/.PS_STORE/config.php

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:
/Library/Preferences/com.apple.SystemLoginItems.plist

It also attempts to add itself to the list of items that open at login:
~/Library/Preferences/loginwindow.plist

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.

It may also use the following program for keylogging functionalities:
LogKext

The Trojan may then capture pictures through the iSight camera by using the following program:
iSightCapture

It may also install a PHP shell and Vine Server application for VNC connections.

The Trojan displays the following dialog box to prompt the user to enter their password in order to steal the information:
Title:
Software Update requires your password.
Message:
A corrupt preference file has been detected and must be repaired. Enter yourpassword to continue:

Recommendations

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.