Medium Large Transport; Low Wing; 2 Turbojet Eng
Flight Crew Air Transport Pilot (ATP)
Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Other / Unknown
Flight Crew Took Evasive Action
Human Factors
We were at the gate. Planned fuel was approximately 15;700 lbs. Fuel on board was  approximately 15;100; well above min fuel; however Captain had asked operations for fuel to be added; probably around XA:45. We were negative APU; therefore the cabin was hot and we needed to start an engine at the gate. At roughly XB:00; with boarding complete and paperwork handed out; we started engine 2 via ground cart. The tug was then attached (or maybe already had been attached); the beacon on; and we called for pushback. Ramp control asked us to hold the push for traffic in the alley behind.While making small-talk with the Captain; we both looked down and saw 'auto x-flow inhibit' status message. This is an indication we're being fueled. I looked back but could not see any fuel truck. The Captain asked the tug driver what was going on- he said we appeared to be being fueled (and expressed surprise as well). The Captain asked him to quickly get them to stop. He also radioed ops to tell them this was not authorized procedure. (We are not allowed to do hot refueling and any refueling requires the passenger door to be open of passengers are onboard). In the end; no harm no foul; but a safety concern and irresponsible behavior of the ground fueling crew; to not notice the airplane was ready to be pushed back and to violate safety protocol.Better communication; and observation by fueler. Although we'd asked for more fuel; we were still able and ready to go with what we had- with an engine running over his shoulder and the beacon on and the jet bridge retracted and the tug attached; there were multiple indications we were not configured for fueling.
Air carrier First Officer reported at the gate in DFW; with an engine running and the beacon on; a fuel truck hooked up and began to fuel the aircraft in violation of company policy.