Apple has developed a Mac OS 9 patch called OT Tuner1.0, to thwart hackers from bombarding OS 9 users with junk traffic.

The pre-patch Mac OS 9 can be abused by intruders, who can generate large volumes of traffic directed at a victim, in response to a small amount of traffic produced by an intruder.

The patch switches off an option in Open Transport 2.5.x which may cause a Mac to respond to certain small network packets with a large Internet ControlMessage Protocol (ICMP) packet. It also prevents Mac OS 9 systems causing denial-of-service issues.