In my world one company has had a monopoly on FTL comms, making large beacons in each inhabited system. This company has worked to prevent knowledge that smaller FTL comms were possible, in order to ensure their monopoly.
The system ansibles work by having a hard coded location and identifier for each comm, which were used to secure them. They only accept messages from known ansibles and generally are securable because the company is regulating every node.
Smaller shipboard ansibles were built as proof-of-concepts within the company at one point, only to be buried when it was decided the tech was a threat to their monopoly. As a incomplete proofs of concept, these shipboard comms were built without any thought to security. For example these comms, unlike the larger system comms, were built to use an ad-hoc registry system where each ansible could register itself with other local ansibles on the fly, but registered ansibles are not properly authenticated! These shipboard ansibles were also only able to broadcast messages within a system; they lack enough power to reach ansibles in other systems.
A certain group -- think of it as something like a large organized pirate fleet with some political extremist views -- has recently had schematics for the shipboard comms leaked to them. The pirates treat the ansibles as black boxes, not understanding the physics or code behind them, but are still able to build and deploy ansibles to their ships, giving them a major tactical advantage in fights where light speed delay usually makes tactics difficult to organize. Our protagonists have captured a small number of these ansibles and are trying to set up their own mini-fleet to resist the pirates'/fanatic group's aggression using them. This includes reverse-engineering the blackbox code of the ansibles to help create exploits to give their side tactical advantages in fights.
All of these battles are happening rapidly with both sides trying to reverse engineer, hack, and patch their ansibles quickly enough to take advantage of, or protect against, exploits as they're discovered, but there isn't enough time to fully learn the code or rewrite more secure code from scratch.
The underlying physics behind the FTL systems is not fully known by either side, and I intend to keep somewhat undefined intentionally to allow me more wiggle room for 'hacks'. So while I have some room to make the physics fit any exploit I like, in general I'm drawing parallels with early wi-fi routers as to how the ansibles function.
I'm looking for more potential exploits that both the hackers and pirates may utilize to gain a tactical advantage. A tactical advantage may mean hearing their enemies comms, 'blocking' their enemies FTL comms, knocking out both sides' comms when desired, replay attacks, whatever.
I'm looking mostly for exploits that both could be quick to write with partially understood code and, ideally, are also relatively quick to patch, so that both sides have to keep coming up with new tricks every few months rather than relying on the same exploit. To make it believable that so many exploits can be figured out so fast, I'm trying to keep a system analogous to the original ARPANET and wireless communication, with exploits being mostly reusing exploits that worked on the old Internet before more secure protocols were made standard.
The first exploit will be eavesdropping on enemy comms most likely, no encryption is built in after all. However, the enemy will figure this out quickly and will start encrypting their messages prior to sending them through the ansible, so that will be patched quickly. I'm more interested in exploits that will occur after that.
I already have a handful of exploits I like, including constant broadcast of gibberish to block both sides' FTL comms, and later one side stopping blocking at brief set periods to allow broadcast of comms during those brief open spots, etc. I'd like help coming up with more exploits to give me more options for what tricks I can have either side perform.