Oooh, this is well into black art territory !
Firstly, ethernet is transformer coupled and balanced so should normally be fairly immune to a lot of external influences. Not the use of the word "should" there
My guess for UPS will be that they went to a supplier and said "how much for a UPS" with nothing more that the load it's supplying. The vast majority of small UPSs are some variation of off-line or line-interactive - ie they just pass the mains through while it's there and they may or may not have any voltage adjustment* or filtering.
You only tend to get into on-line stuff when you get into the bigger (and more expensive) sizes. The 12kVA unit at work cost around £6k, an equivalent APC unit (Symmetra) tips the scales at around £13k
But I digress.
If the OP is in an area prone to storms, then yes, some form of filtering/surge protection could well be in order - you don't need a direct lightning strike to cause big problems. When a customer phones you to say there was a bang and now there's a burning smell coming from the cupboard where the server lives then you know something happened. But to be fully effective, you must route
ALL circuits to the installation through one point - it's not so much a case of preventing a surge getting in, but making sure that it can't have different effects on different bits of the system.
For example, a previous boss lived in a house in the sticks, and was forever replacing the fax machine - but not the basic phones. The problem is that a common mode surge down either mains or phone line gets converted to an unbalanced surge between phone line and mains. So you need to route both phone line and power through one point, so surge protectors on both can share a common point which you ground as best you can. You'll still get a fair bit of surge getting to the equipment - bit it's now common mode across all parts of it, and that would be the case even if the earthing wasn't too good.
Some people may recognise a similarity with "earthing" and "equipotential bonding" with regard to mains supplies, water pipes etc.
I'll qualify that "earthing not too good" bit by pointing out that with lightning induces surges, the rise time can be such that the inductance of a few meters of 10mm2 cable renders it effectively an open circuit to the spike. That's why you need to bring all protected circuits to one point - if you install protectors on different circuits at different places (eg phones come it at opposite end of building to power) then the cable connecting them may as well not be there if considering lightning induced surges.
I've seen a very good demonstration (not involving lightning) of this. The test rig was a small DC motor, and an amplifier to pick up the noise from it. The test rig included a very expensive (military) filter in the supply to the motor, which was rendered ineffective by about 1 foot of large earth strap (probably in excess of 10mm2). The demonstration simply involved pushing on the filter (mounted on shock mounts) so it's mounting bolts earthed it directly to the metal plate the rig was on and the noise disappeared.
* At my last job we put in an APC Matrix 5000. A heavy beast with a tap changing facility which I;d occasionally hear it operating. Gave me "a bit of a start" the first time I heard it - sounded like a few shorted turns for a couple of seconds !
