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TA15-105A: Simda Botnet

Original release date: April 15, 2015

Systems Affected

Microsoft Windows

Overview

The Simda botnet – a network of computers infected with self-propagating malware – has compromised more than 770,000 computers worldwide [1].

The United States Department of Homeland Security (DHS), in collaboration with Interpol and the Federal Bureau of Investigation (FBI), has released this Technical Alert to provide further information about the Simda botnet, along with prevention and mitigation recommendations.

Description

Since 2009, cyber criminals have been targeting computers with unpatched software and compromising them with Simda malware [2]. This malware may re-route a user’s Internet traffic to websites under criminal control or can be used to install additional malware. 

The malicious actors control the network of compromised systems (botnet) through backdoors, giving them remote access to carry out additional attacks or to “sell” control of the botnet to other criminals [1]. The backdoors also morph their presence every few hours, allowing low anti-virus detection rates and the means for stealthy operation [3].    

Impact

A system infected with Simda may allow cyber criminals to harvest user credentials, including banking information; install additional malware; or cause other malicious attacks. The breadth of infected systems allows Simda operators flexibility to load custom features tailored to individual targets.

Solution

Users are recommended to take the following actions to remediate Simda infections:

  • Use and maintain anti-virus software - Anti-virus software recognizes and protects your computer against most known viruses. It is important to keep your anti-virus software up-to-date (see Understanding Anti-Virus Software for more information).
  • Change your passwords - Your original passwords may have been compromised during the infection, so you should change them (see Choosing and Protecting Passwords for more information).
  • Keep your operating system and application software up-to-date - Install software patches so that attackers cannot take advantage of known problems or vulnerabilities. Many operating systems offer automatic updates. If this option is available, you should enable it (see Understanding Patches for more information).
  • Use anti-malware tools - Using a legitimate program that identifies and removes malware can help eliminate an infection. Users can consider employing a remediation tool (examples below) that will help with the removal of Simda from your system.

          Kaspersky Lab : http://www.kaspersky.com/security-scan

          Microsoft: http://www.microsoft.com/security/scanner/en-us/default.aspx

          Trend Micro: http://housecall.trendmicro.com/

  • Check to see if your system is infected – The link below offers a simplified check for beginners and a manual check for experts.

          Cyber Defense Institute:  http://www.cyberdefense.jp/simda/

The above are examples only and do not constitute an exhaustive list. The U.S. government does not endorse or support any particular product or vendor.

References

Revision History

  • April 15, 2015: Initial Release

This product is provided subject to this Notification and this Privacy & Use policy.


TA15-103A: DNS Zone Transfer AXFR Requests May Leak Domain Information

Original release date: April 13, 2015 | Last revised: April 15, 2015

Systems Affected

Misconfigured Domain Name System (DNS) servers that respond to global Asynchronous Transfer Full Range (AXFR) requests.

Overview

A remote unauthenticated user may request a DNS zone transfer from a public-facing DNS server. If improperly configured, the DNS server may respond with information about the requested zone, revealing internal network structure and potentially sensitive information.

Description

AXFR is a protocol for “zone transfers” for replication of DNS data across multiple DNS servers. Unlike normal DNS queries that require the user to know some DNS information ahead of time, AXFR queries reveal resource records including subdomain names [1]. Because a zone transfer is a single query, it could be used by an adversary to efficiently obtain DNS data.  

A well-known problem with DNS is that zone transfer requests can disclose domain information; for example, see CVE-1999-0532 and a 2002 CERT/CC white paper [2][3]. However, the issue has regained attention due to recent Internet scans still showing a large number of misconfigured DNS servers. Open-source, tested scripts are now available to scan for the possible exposure, increasing the likelihood of exploitation [4].

Impact

A remote unauthenticated user may observe internal network structure, learning information useful for other directed attacks.

Solution

Configure your DNS server to respond only to zone transfer (AXFR) requests from known IP addresses. Many open-source resources give instructions on reconfiguring your DNS server. For example, see this AXFR article for information on testing and fixing the configuration of a BIND DNS server. US-CERT does not endorse or support any particular product or vendor.

References

Revision History

  • April 13, 2015: Initial Release

This product is provided subject to this Notification and this Privacy & Use policy.


TA15-098A: AAEH

Original release date: April 09, 2015

Systems Affected

  • Microsoft Windows 95, 98, Me, 2000, XP, Vista, 7, and 8
  • Microsoft Server 2003, Server 2008, Server 2008 R2, and Server 2012

Overview

AAEH is a family of polymorphic downloaders created with the primary purpose of downloading other malware, including password stealers, rootkits, fake antivirus, and ransomware.

The United States Department of Homeland Security (DHS), in collaboration with Europol, the Federal Bureau of Investigation (FBI) and the Department of Justice (DOJ), released this Technical Alert to provide further information about the AAEH botnet, along with prevention and mitigation recommendations.

Description

AAEH is often propagated across networks, removable drives (USB/CD/DVD), and through ZIP and RAR archive files. Also known as VObfus, VBObfus, Beebone or Changeup, the polymorphic malware has the ability to change its form with every infection. AAEH is a polymorphic downloader with more than 2 million unique samples. Once installed, it morphs every few hours and rapidly spreads across the network.  AAEH has been used to download other malware families, such as Zeus, Cryptolocker, ZeroAccess, and Cutwail.

Impact

A system infected with AAEH may be employed to distribute malicious software, harvest users' credentials for online services, including banking services, and extort money from users by encrypting key files and then demanding payment in order to return the files to a readable state. AAEH is capable of defeating anti-virus products by blocking connections to IP addresses associated with Internet security companies and by preventing anti-virus tools from running on infected machines.  

Solution

Users are recommended to take the following actions to remediate AAEH infections:

References

Revision History

  • April 9, 2015: Initial Release

This product is provided subject to this Notification and this Privacy & Use policy.


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