I've already asked this question on networkengineering.stackexchange.com, but unfortunately it was marked as Offtopic there.
As far as im concerned the CSMA/CD and the CSMA/CA standard rely on the compliance of the protocol standard of the hosts connected to the communication channel. For example: If a collision is detected in Ethernet, all involved hosts wait for a random time and try after that to send their data again - at least if the channel is not already used (carrier sensing). Another example: In the WLAN-Standard of DCF the hosts who want to send something compete with each other for channel access by waiting a random amount of time. This seems to me on the first look like a good idea, because if every host really does what the standard dictates, its quite fair for everyone who is involved. But lets just say there is an attacker connected to the channel who doesn't care about the protocol standards in the data link layer. If he is involved in a collision in Ethernet, then he simply cheats by waiting the lowest amount of time. If he needs to compete with other hosts in Wifi for channel access, he does the same, so that he is always the first one who can send. If everybody did this, the network would be congested.
€dit - to be hopefully more clear: I just think about if one could achieve a higher data rate in a network (for example in the Wifi of an hotel/cafe) by ignoring back off times (https://en.wikipedia.org/wiki/Exponential_backoff) in the data link layer.
I think for doing this, one just has to modify the network driver. But is it really that easy or have i forgotten to consider something important? And if it's really that easy, why is it not done in practice? (At least I've never heard of it) Greetings