The desktop
freezes with a warning message from the local police that the user has violated
the law by visits to pornographic sites and has been fined 300 dollars or local
equivalent. Until the fine is paid, either all critical files on the desktop
have been encrypted or access to the system barred via a locked screen. Victims
promptly pay up, running scared of the threat of legal action and the resulting
public humiliation of having being caught viewing porn. The victim does not
realize that he was set-up by a small group of cyber criminals who specialize
in setting up malicious sites that when visited, infect desktops, with a
malicious piece of malware known as Ransomware.
Faced with no option but to pay, as it is very hard to crack encryption
or to avoid the embarrassment that could follow, victims pay – thereby making
the crime profitable.
Ransomware as
the name suggests is a piece of malicious software that either encrypts files on
or locks screens to shut access to a desktop, tablet or mobile phone until a
ransom is paid to obtain a secret key used to decrypt files or to unlock the
device.
In case of
desktops the malicious software is usually surreptitiously downloaded and
installed from malicious or legitimate website infected with malicious code.
The user is unaware that the system has been infected until the files have been
encrypted and the malware popped-up messages demanding ransom. Surreptitious download and installation
without a user’s acceptance is possible due to vulnerabilities in browsers and made
easier if the user possessed administrative rights to install applications. Due
to the design of the operating system used in mobiles and tablets, malware once
downloaded requires user intervention to install the application.
Cybercriminals disguise these applications as system updates or fake versions
of popular applications, which users believe are genuine and allow their
installation.
How to prevent Ransomware infections
Recovering
from a ransomware attack is very difficult, due to the hard to crack
encryption. Prevention and regular offline back-ups remain the best defense.
Antivirus software alone will not be effective due to the fast emerging
variations of ransomware programs and attack methods. A few useful tips to help
prevention are:
1.
Restrict
administrative rights
2.
Restrict
use of Java, flash and other such programs to trusted sites. This can be done
through browser settings
3.
Check
to see if the pop-ups are genuine. Updates should come from vendor sites
4.
Download
apps from genuine app stores
5.
Keep
an offline back-up of your data ( online backup can be encrypted by the
malware, particularly if automated)
6.
Keep
your system patch levels updated
7.
Use
antivirus software which will help control access to malicious sites and delete
known instances of ransomware.
How to Recover from Ransomware
infections
A typical ransom
requested is usually below 500$, in the form of vouchers that can be used to buy goods and
services online and even
if paid there is a good chance that system is not unlocked. It is therefore best
to be prepared to lose the data on the device. The two articles (links below)
are excellent resources to recover from Ransomware Attacks
Decrypting the Crypto Locker – a tool from FireEye and Fox-IT to decrypt files
encrypted by Cryptolocker, a dangerous strain of ransomware
One of the
frequent methods used to recover is by paying the ransom, and if through this the
users files were successfully decrypted, it is best to save critical data, wipe
the disk clean and reinstall a fresh copy of the operating system and other
application executables, as there could be further residual malware of a different
type. And then there obviously remains the task of preventing further
infections.