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[tlug] [OT] National Cyber Awareness System: TA13-309A: CryptoLocker Ransomware Infections

Not Linux, but thought this might be of interest nonetheless:


National Cyber Awareness System:
TA13-309A: CryptoLocker Ransomware Infections
11/05/2013 10:58 AM EST

Original release date: November 05, 2013 | Last revised: November 13, 2013

Systems Affected:
Microsoft Windows systems running Windows 8, Windows 7, Vista, and XP
operating systems


US-CERT is aware of a malware campaign that surfaced in 2013 and is
associated with an increasing number of ransomware infections.
CryptoLocker is a new variant of ransomware that restricts access to
infected computers and demands the victim provide a payment to the
attackers in order to decrypt and recover their files. As of this
time, the primary means of infection appears to be phishing emails
containing malicious attachments. Description

CryptoLocker appears to have been spreading through fake emails
designed to mimic the look of legitimate businesses and through phony
FedEx and UPS tracking notices. In addition, there have been reports
that some victims saw the malware appear following after a previous
infection from one of several botnets frequently leveraged in the
cyber-criminal underground.


The malware has the ability to find and encrypt files located within
shared network drives, USB drives, external hard drives, network file
shares and even some cloud storage drives. If one computer on a
network becomes infected, mapped network drives could also become
infected. CryptoLocker then connects to the attackers’ command and
control (C2) server to deposit the asymmetric private encryption key
out of the victim’s reach.

Victim files are encrypted using asymmetric encryption. Asymmetric
encryption uses two different keys for encrypting and decrypting
messages. Asymmetric encryption is a more secure form of encryption as
only one party is aware of the private key, while both sides know the
public key.

While victims are told they have three days to pay the attacker
through a third-party payment method (MoneyPak, Bitcoin), some victims
have claimed online that they paid the attackers and did not receive
the promised decryption key. US-CERT and DHS encourage users and
administrators experiencing a ransomware infection NOT to respond to
extortion attempts by attempting payment and instead to report the
incident to the FBI at the Internet Crime Complaint Center (IC3) .


US-CERT recommends users and administrators take the following
preventative measures to protect their computer networks from a
CryptoLocker infection:

    * Do not follow unsolicited web links in email messages or submit
any information to webpages in links
    * Use caution when opening email attachments. Refer to the
Security Tip Using Caution with Email Attachments for more information
on safely handling email attachments
    * Maintain up-to-date anti-virus software
    * Perform regular backups of all systems to limit the impact of
data and/or system loss
    * Apply changes to your Intrusion Detection/Prevention Systems and
Firewalls to detect any known malicious activity
    * Secure open-share drives by only allowing connections from
authorized users
    * Keep your operating system and software up-to-date with the latest patches
    * Refer to the Recognizing and Avoiding Email Scams (pdf) document
for more information on avoiding email scams
    * Refer to the Security Tip Avoiding Social Engineering and
Phishing Attacks for more information on social engineering attacks


US-CERT suggests the following possible mitigation steps that users
and administrators can implement, if you believe your computer has
been infected with CryptoLocker malware:

    * Immediately disconnect the infected system from the wireless or
wired network. This may prevent the malware from further encrypting
any more files on the network
    * Users who are infected should change all passwords AFTER
removing the malware from their system
    * Users who are infected with the malware should consult with a
reputable security expert to assist in removing the malware, or users
can retrieve encrypted files by the following methods:
        * Restore from backup,
        * Restore from a shadow copy or
        * Perform a system restore.

    * CryptoLocker Virus: New Malware Holds Computers For Ransom,
Demands $300 Within 100 Hours And Threatens To Encrypt Hard Drive
    * CryptoLocker Wants Your Money!
    * CryptoLocker ransomware – see how it works, learn about
prevention, cleanup and recovery
    * Microsoft Support – Description of the Software Restriction
Policies in Windows XP
    * Microsoft Software Restriction Policies Technical Reference –
How Software Restriction Policies Work
    * CryptoLocker Ransomware Information Guide and FAQ

Revision History

    * Initial
    * November 13, 2013: Update to Systems Affected (inclusion of Windows 8)


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