Complicated EM field, that works subtlety to cause catastrophic reactions in machines.
A Sabotage field, is a EM field wherein a complex pattern of signals/pulses is generated. These pulses, repeat themselves in a 3-D pattern and cause mostly random and small scale malfunctions in electronic devices. Terminals may lag and fluctuate, sensors may give incorrect readings, but as they continue, they gradually grow more frequent and worse.
The more complicated and circuit based the device, the more likely it is to be affected.
Their effects on mechanical beings varies, for some purely mechanical mechanoids, the field is the equivalent to a localized plague. For Spark Based mechanoids, the effects may be detrimental but not immediately fatal.
What makes the field so dangerous is that it can be difficult to detect, as devices scanning for it, will often be within its sphere of influence and and its pulse pattern was designed to be easily missed.
However, they are not readily common, as they effect both sides equally and require long, long calculations to figure out a pattern for the correct situation.