Online users who have received unexpected email messages with attached files with names ending with .arj are asked not to open them. This is because the attachments are compressed files that may contain malware, malicious programs or viruses. And, any attempt to open the malicious attachments will result in the recipients getting their computers infected with a virus, Trojan horse, spyware, ransomware or other malware.
A Malicious .ARJ Email Message
Sun 9/9/2018 10:12 PM
From: "Wu Xueming"
Attachments: OrderList.arj (428 KB)
We have gone through your samples from a partner and Here attached is our Order List.
Please do bear in mind that we are very much in need of this order,quote your competitive prices, also let us know your MOQ,FOB.
If you can finish on or before 30 days, we will make another order immediately
The ".ARJ" compression is similar to ZIP which is the most popular file compression or archive formats.
Cyber criminals usually store their malware in compressed files to help prevent antivirus software from detecting them. In other words, they do it because the compressed malicious email attachments may bypass the recipients' antivirus software.
What is a .ARJ file?
ARJ (Archived by Robert Jung) is a software tool designed by Robert K. Jung for creating high-efficiency compressed file archives.