Compressed files like .rar are a common vector for malware because they can hide executable threats from some antivirus scanners until extracted. WinRAR vulnerability exploited by two different groups
Various technical tools, such as the MVS Toolkit for web service export/import or inventory management apps like The ToolKit , are often distributed in compressed formats. Security Risks and Vulnerabilities Download Toolkit rar
Depending on what you are looking for, a "Toolkit .rar" could be one of the following: Compressed files like