All malware is bad, but ransomware is particularly insidious--ask any ransomware victim. That's why a new attack scheme called "Pacman" has raised alarms, because it's even nastier than usual. Think of the classic Pac-Man game's voracious yellow ball, chomping up all of your files. It takes only one click to infect a vulnerable PC, and the attack gives victims only 24 hours to pay the ransom in Bitcoins or risk losing all of the compromised data.
The current attack is particularly effective because it's so convincing. Pacman's first victims have been Danish chiropractors, who received emails with a subject line of "Possible new patient." Unlike the laughably amateurish writing of some phishing emails, this one was written in perfect Danish and included Dropbox links to MRI and CT scans of the problem for the doctor to review--except the links launched ransomware instead.
When a victim clicks the link, the pacman.exe file is extracted and begins to encrypt data on the infected system. The files are marked with a new file extension of ".ENCRYPTED," and the Windows desktop is replaced with the ransom demand. Pacman even hedges itself by installing a keystroke logging component and a "kill" process that can shut down Windows operating system functions such as taskmgr, cmd, regedit, making it very difficult to analyze or remove the malware.
The attack is built in Microsoft's .NET programming framework, so it requires that the target machine have the .NET framework installed as well. Most Windows machines have .NET framework by default.
Pacman's just getting warmed up
Pacman's initial victim pool is small, but we can assume it will spread. KnowBe4 CEO Stu Sjouwerman points out that all of the tens of millions of records that have been compromised in data breaches make it significantly easier for attackers to compose more effective spear phishing attacks.
Sjouwerman advises that businesses block access to Dropbox, because the malicious links and ransomware files use the Dropbox domain. Unless a business happens to subscribe to a Dropbox business plan, blocking Dropbox makes sense anyway. From a compliance and data protection perspective, users should not be storing or sharing company data on personal Dropbox accounts.
The most critical thing for individuals is awareness and common sense. Well-executed spear phishing attacks can be very convincing. Be skeptical of emails from unknown sources, or from known sources that don't typically email you. Think twice (or three times) before you click a link.
If an email appears legitimate, the prudent course is to delete the email and open a separate browser to visit the website directly. You can also pick up the phone and call the alleged source of the email for clarification or more information, rather than risking a ransomware infection with just one click.