1. Symantec/
  2. Security Response/
  3. Infostealer


Risk Level 1: Very Low

December 8, 1997
May 21, 2013 1:58:18 PM
Infection Length:
Systems Affected:
Infostealer is a detection name used by Symantec to identify malicious software programs that gathers confidential information from the compromised computer.

Background information

Back in the day, Infostealers were known by several names including Keyloggers and Password Stealers. These malicious keystroke capturing programs were created to steal login credentials and passwords, product keys for software programs, and game credentials and passwords. At that time, stealing information wasn't a big market and money-maker. Games weren't online then, being played solely on the computer so giving friends access to software products or computer game access was one way of getting recognition for the malware author.

Eventually, malware authors realized that there was money to be made by stealing particular types of information. Identity theft is big news these days for a very good reason. According to the U.S. Treasury Dept., every three seconds, an identity is stolen online.

The virtual world has become just as busy as the real world. Games are now online. Shopping went online. Banking is conveniently online. Identity theft has now gone online and that criminal activity is a real gold mine. With the popularity of the Internet, capturing the login and password for online mail programs went from a petty means to harass a user or prove malware writing superiority to a financial windfall. Collecting email addresses is now a major business opportunity when selling this information to spammers.

Remote attackers creating botnets use the stolen computer information to continue expanding their networks. As this information can also be bought and sold, there is a profit motive driving the creation of botnets.

Who creates Infostealers?

Infostealers are created by malware authors intending to make a profit by gathering various types of information and selling them to other criminals.

The stolen information can be worth considerable sums of money depending on the details involved. For example in 2008 it was reported by Symantec researchers that some of the most popular items of information sold in the underground economy are:

  • Credit card information - for between US$0.06 - $30 each.
  • Bank accounts - for between US$10 - $1000 each depending on the balance.
  • Email accounts - for between US$0.10 - $100 each

Given the sums of money involved for each item, it is clear why the malware authors try to scale their operations to gather as much information as possible in order to maximize profit potential.

What can Infostealers do?
Infostealers gather information by using several techniques. The most common techniques include the following:
  • Log key strokes
  • Capture screen shots and Web cam images
  • Monitor Internet activity, often for specific financial web sites and then injecting extra fields in to the forms displayed in the browser

The stolen information may be stored locally so that it can be retrieved later or it can be sent to a remote location where it can be accessed by an attacker. It is often encrypted before posting it to the malware author.

What is stolen?
Infostealers are configured to gather and sometimes send various types of information. This will depend on the needs and market niche of the remote attacker. Some malware authors focus on specific financial information and identity theft for profit, while others will steal information related to the compromised computer. Such information may seem innocuous, but in the hands of a botnet master can lead to more criminal activity.

Some of the financial information stolen by Infostealers include the following:
  • Bank account information and passwords
  • Credit card numbers
  • Date of birth
  • Names
  • Phone numbers
  • Security question details
  • Social Security Numbers

Targeted sensitive computer information stolen by Infostealers include the following:
  • Authentication cookies
  • Computer name/Host name
  • DNS details
  • General Operating System information
  • Geographic and browser version information
  • IP address
  • Network traffic information
  • Private keys from system certificates
  • Security-related information
  • Software Information
  • URLs visited

These Trojans may also attempt to steal confidential login credentials such as the following:
  • Email addresses
  • Login credentials/passwords for certain web sites
  • Login details for FTP, IRC, POP3 email, and IMAP email
  • Outlook account information
  • User names and passwords

Are there any tell-tale signs?
Infostealers are often designed to stay hidden to give the remote attacker as much information as possible so generally speaking, there will be no obvious tell-tale signs.

What are the risks?
With confidential and sensitive information at stake, there is no minimal risk with an Infostealer. Identity theft is the highest risk posed by these Trojans and is a risk considered to be personally damaging to a user. Stealing personally identifiable information for profit has become a huge underground market with a devastating financial costs to the victims.

Are you at risk for identity theft? Check your risk assessment with Symantec's risk assessment tool.

What can I do to minimize the risks?

As a general rule, users should always run up-to-date antivirus software with real-time protection such as Norton Antivirus, Norton Internet Security, Norton 360 or Symantec Endpoint Protection. In addition, a firewall -- or better still, an Intrusion Prevention System (IPS) -- will help to block download activities initiated by these types of malicious programs. Program controls such as those found in Symantec Endpoint Protection can also help to prevent programs such as these from executing in the first place.

How can I find out more?
Advanced users can submit a sample to Threat Expert to obtain a detailed report of the system and file system changes caused by a threat.


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.
Writeup By: Angela Thigpen
Summary| Technical Details| Removal

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