NCCIC has received multiple reports of ransomware infections worldwide. Ransomware is a type of malicious software that infects and restricts access to a computer until a ransom is paid. Although there are other methods of delivery, ransomware is frequently delivered through phishing emails and exploits unpatched vulnerabilities in software.
Phishing emails are crafted to appear as though they have been sent from a legitimate organization or known individual. These emails often entice users to click on a link or open an attachment containing malicious code. After the code is run, your computer may become infected with malware.
A commitment to cyber hygiene and best practices is critical to protecting organizations and users from cyber threats, including malware.
In advice specific to recent ransomware threats, users should:
- Perform frequent backups of system and important files and verify those backups regularly. If ransomware affects your system, you can restore your system to its previous state with any files unaffected by ransomware.
- The safest practice is to store backups on a separate device that cannot be accessed from a network. (For additional information, see the Software Engineering Institute’s blog post on Ransomware.)
- Be careful when clicking directly on links in emails, even if the sender appears to be known; attempt to verify web addresses independently (e.g., contact your organization's helpdesk or search the Internet for the main website of the organization or topic mentioned in the email).
- Exercise caution when opening email attachments. Be particularly wary of compressed or ZIP file attachments.
- Follow best practices for Server Message Block (SMB) and update to the latest version immediately. (See US-CERT’s SMBv1 Current Activity for more information.)
For general best practices on patching and phishing, users should:
- Ensure that your applications and operating system has been patched with the latest updates. Vulnerable applications and operating systems are the target of most attacks. (See Understanding Patches.)
- Be suspicious of unsolicited phone calls, visits, or email messages from individuals asking about employees or other internal information. If an unknown individual claims to be from a legitimate organization, try to verify his or her identity directly with the company.
- Avoid providing personal information or information about your organization, including its structure or networks, unless you are certain of a person's authority to have the information.
- Avoid revealing personal or financial information in email, and do not respond to email solicitations for this information. This includes following links sent in email.
- Be cautious about sending sensitive information over the Internet before checking a website's security. (See Protecting Your Privacy.)
- Pay attention to the URL of a website. Malicious websites may look identical to a legitimate site, but the URL may use a variation in spelling or a different domain (e.g., .com vs. .net).
- If you are unsure whether an email request is legitimate, try to verify it by contacting the company directly. Do not use contact information provided on a website connected to the request; instead, check previous statements for contact information. Information about known phishing attacks is also available online from anti-phishing groups such as the APWG.
- Install and maintain anti-virus software, firewalls, and email filters to reduce some of this traffic. (See Understanding Firewalls, Understanding Anti-Virus Software, and Reducing Spam for additional information.)
If you believe that you have been a victim of a phishing attack or ransomware infection, immediately report the incident to your information technology (IT) helpdesk or security office.