Discovered: January 27, 2009
Updated: January 27, 2009 7:51:16 PM
Also Known As: OSX/iWorkS-B [Sophos], OSX/IWService.b [McAfee], Backdoor.OSX.iWorm.c [Kaspersky]
Infection Length: 413,604 bytes
Systems Affected: Mac
OSX.Iservice.B is a Trojan horse that runs on Mac OS X and opens a back door on the compromised computer.
The Trojan is shared through BitTorrent and is bundled in a .zip file as a crack with a copy of the Adobe Photoshop application.
The above bundle has the following file name and is 1,059,954,851 bytes (1,010 MB) in size:
Adobe Photoshop CS4 11.0 Extended (Mac OS X) Includes Crack+serial (Works 100%).zip
The bundle contains the following legitimate copy of the Adobe Photoshop application:
Adobe Photoshop CS4 11.0 Retail.dmg
It also contains the following files:
Adobe CS4 Crack(intel)
PS CS4 Serial Number *(Mac).pdf
When 'Adobe CS4 Crack(intel)' is executed, the Trojan extracts its main component to the following location:
/var/temp/[RANDOM FILE NAME]
It will then prompt the user for root credentials in order to execute it.
The Trojan will then open the real crack for the Adobe Photoshop application.
Note: The malicious file is a Universal Binary designed to run both on PowerPC and x86 architectures.
Next, the Trojan determines if the session is running with root privileges. If not, the threat exits.
The Trojan creates the following folder if it did not execute from the DivX file:
The Trojan copies itself as the following file:
It modifies the following files so that it runs every time the computer starts:
Next, the Trojan restarts itself from the /System/Library/StartupItems/DivX/DivX folder and decrypts its configuration file which is encrypted with the AES algorithm.
It then opens a back door on the compromised computer and may contact the following hosts in order to receive further commands from the remote attacker:
The remote attacker may use the following remote commands:
Note: The network traffic is encrypted with AES.
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.
- Update the virus definitions.
- Run a full system scan and repair or delete all the files detected.
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).
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: Mario Ballano Barcena