The attack scenario is best described as Instant Messenger Applications, and the measure that could have prevented it is verifying the sender’s identity before opening any files. Instant Messenger Applications are communication tools that allow users to exchange text, voice, video, and file messages in real time. However, they can also be used as attack vectors for spreading malware, such as viruses, worms, or Trojans, by exploiting the trust and familiarity between the users. In this scenario, the attacker compromised one of the team member’s messenger account and used it to send malicious files to the other team members, who may have opened them without suspicion, thus infecting their systems. This type of attack is also known as an instant messaging worm12.

To prevent this type of attack, the users should verify the sender’s identity before opening any files sent through instant messenger applications. This can be done by checking the sender’s profile, asking for confirmation, or using a secure channel. Additionally, the users should also follow other security tips, such as using strong passwords, updating the application software, scanning the files with antivirus software, and reporting any suspicious activity34.