Troj_Gaara.A is the Trend Micro detection for a proof-of-concept (PoC) malware that targets Texas Instruments TI-89 graphing calculators. It infects TI-89 assembly files by appending its code on them. It also hooks itself to a certain function in the calculator that enables it to run when that particular function is called.

It can clear the screen and display the string t89.GAARA under a certain condition.

Note that this malware does not have any ability to propagate. Infection can only occur if it is deliberately run on a TI-89.

This malware is proof that any electronic device with sufficient computing power and functionality can be utilized as an execution vector for malicious code.

Technical details can be found at this Trend Micro page.