A bit of nVIR-A experience, and a new test application

Infection compatibility

We had this week a rather interesting thing happen by accident, which was rather unusual: While trying out a couple potential test applications with the emulator, we ran into an application which was infected by nVIR A type virus ( https://en.wikipedia.org/wiki/NVIR ). What makes this interesting, is that it apparently was able to infect the System file of that application’s bundle, as we now have near-complete resource write support:

Above is partial output of the System file’s resource map debug dump (and Rezilla screenshot of infected System file), and the ‘nVIR’ and ‘INIT’ resources were actually written into the System file by the virus in infected application – and the system resource map seemed to be (mostly) still functional! I only found this out because a bug in resource writing corrupted Geneva font, causing the infected application to crash. A kind of controversial achievement, having good enough compatibility for even viruses to work in the toolbox emulation…

One of the positive sides of the current per-application bundling of files as isolated file systems, is that the infection never was able to break out of the application bundle. We have also scrubbed through all the disk images and Mac files downloaded we use for development and testing, to make sure there will not be any risk of infection at later time (and run Disinfectant on the source Macs/emulators regularly). These viruses are ancient, but can awake up at any time it seems…

New test application: IAGO

After we got the infection sorted out and everything back to normal, we experimented with a couple of new test applications, and found out that IAGO, which is a public domain game written by David Reed in 1984.

We were able to identify one bug in ROXLI.L instruction, which caused the game timer to not advance correctly. After it was fixed, the game works as smoothly as it does on a (fast) real Macs. It is now also available for testing as application bundle in the downloads section.