Ransomware attacks -- where online extortionists encrypt data on a victim’s computer and then demand a fee for unlocking it -- started off mainly as a consumer problem but increasingly is hitting businesses and government entities as well.
The trend has significantly heightened the need for organizations to have measures in place for blocking the threat and for mitigating damage to the extent possible. Most security experts agree that it is almost impossible to recover data that might have been encrypted in a ransomware attack without access to the decryption keys, or to a backup copy of the affected data.
So the focus has to be on prevention.
“[Ransomware] is evil because if implemented correctly by the attackers … it is very difficult to recover the data on the machine,” says Engin Kirda, co-founder and chief architect at security vendor Lastline. “The key difference of this type of malware compared to traditional malware is that you often know that you have been infected because the malware tells you this."
Having a robust data backup process can go a long way in blunting the threat posed by ransomware. In fact, it is often the only way to recover data if you are unwilling to pay the ransom demanded by an extortionist. But there are other measures that organizations can take as well, including the following:
Authenticate In-Bound Email
Email is a commonly used method to distribute ransomware. Attackers target victims with cleverly spoofed emails that appear to originate from someone the victim knows. The emails have malicious attachments which when opened results in the ransomware being downloaded on the victim’s system.
One of the most effective ways for an organization to blunt this threat is to validate the origin of an email before it is delivered to the intended recipient, says Craig Spiezle, executive director and president of the Online Trust Alliance (OTA).
Implementing sender identity technologies like Sender Policy Framework (SPF), Domain Message Authentication Reporting and Conformance (DMARC), and DomainKeys Identified Mail (DKIM) can all protect organizations against spear phishing, business email compromise, and other threats posed by spoofed email, Spiezle says. They work by validating the IP address and domain of the server from which an email originates.
“Unfortunately, most corporations are not authenticating inbound mail,” Spiezle says. And when they do, the policies are not strong enough. For example, emails that fail authentication tests are often simply quarantined or sent to a junk folder. Instead, “corporations that have sensitive information should have a reject policy for email that fail,” authentication tests, he says.
Protect Your Email Servers
Sender authentication can mitigate the risk of ransomware being delivered via email. But that alone is not sufficient, says Craig Young, security researcher at Tripwire. If you haven’t done so already, protect mail servers by scanning all stored, incoming, and outgoing mail. Such scanning can help organizations detect threats that might have evaded perimeter defenses or infiltrated the network via compromised systems and internal email. Numerous tools are available for scanning email servers for security threats. Take advantage of them, he says.
“Email authentication is a good measure to have,” Young says. “But there’s always a chance that a legitimate email server is used to send out spam emails,” and other malware, he says.
Add Ad Blocking
In addition to emails, attackers often distribute ransomware through malicious advertisements served up to users when they visit certain sites. Malvertisements allow attackers to target victims based on their browsing habits, location, demographic information, device characteristics, and other criteria. Ransomware served up via watering-hole attacks often tend to be more dangerous than random attacks because they are targeted at victims which the attackers know have the capability to pay up.
Blocking ads from being delivered on user systems or preventing users from accessing certain sites can diminish this risk somewhat, Spiezle says. Organizations that want to accommodate unrestricted access to the Internet for employees might consider implementing a separate network for them to do so, he says, pointing to one government contractor that has taken this approach.
Monitor File Activity
With ransomware, an attack against an individual can quickly escalate into an attack against the enterprise, says Amichai Shulman, chief technology officer at Imperva. Many ransomware tools have the ability to encrypt not just the hard drive of a system, but also any shared files.
In fact, rapid file overwriting is one of the clearest markers of ransomware on your network, he says. So using a tool to monitor file activity is a good idea, says Shulman, whose company sells an activity-monitoring tool.
“If you are constantly monitoring access to file servers, there are very distinctive patterns that you can look for in order to detect ransomware,” on an endpoint, he says.
Such early detection can help organizations contain the damage that a ransomware tool can wreak, he says. “The advantage is that you can go quickly into quarantine mode for the infected machine and make sure it doesn’t connect to any other file server,” in the enterprise.
Keep Your Response Plan Handy
Time is critical for an organization faced with a ransomware deadline. Online extortionists typically give organizations a very specific time limit within which to pay -- fter which they sharply increase the ransom amount. Attackers have gotten increasingly better at knowing what an organization can afford and knowing exactly when to strike, Spiezle says. They deliberately don’t give enough time for an organization to figure out if it can try and unlock the data without paying any ransom.
So it is important to have a plan in place describing what needs to happen in the event of a ransomware attack. Do an inventory of your critical data assets, know where it is located, and evaluate that impact of any loss or unavailability of that data.
“One of the worst things is the chaos that ensues during an incident like this. Emotions run high, people don’t have the answers and they are scrambling,” to respond. he says. “The last thing you want is to be doing a Google search for a local forensics experts at 2am on a Saturday morning.”
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