Air carrier pilot reported false terrain alerts and numerous system errors due to GPS interference on a flight while in the vicinity of the Middle East region.

Narrative

CA/FO were PF and PM Day 0 XA:51Z westbound FL 360 approaching KITOK intersection 'ADS-B OUT' EICAS message displayed with 'ADS-B OUT DATA R and ADS-B OUT DATA L' status messages. At XB:03Z 'TERR POS' EICAS message also displayed on PFD. Egyptian controllers were difficult to hear as interference on the frequency similar to a stuck mic seemed to be degrading their signal. They were also issuing multiple vectors to aircraft in their sector. At about XB:10Z we noticed aircraft entered a left bank when it should have been tracking straight ahead toward SERMA. Selected HDG select to correct back toward SERMA. Just short of SERMA 'INERTIAL' was displayed. At about XB:15Z DME-DME was displayed and we received a GPWS audible 'TERRAIN TERRAIN PULL UP PULL UP' repetitive warning with 'TERRAIN' also displayed in red on the ND (Navigation Display). FO's ND terrain display was completely corrupted with erroneous data roughly depicting the Greek coastline.OVRD was selected on GPWS to eliminate erroneous data. CA's EFB display showed aircraft far right of airway centerline in LCCC FIR while FO's EFB display was correct. Subsequent selection of POS on CA's ND showed both IRU (Inertial Reference Unit) positions right of course and the POS REF display showed IRU L as 'ACTUAL 12.4NM' GPS-IRU R 'ACTUAL 0.04NM' Wrote up GPWS TERR OVRD message as we left the GPWS in OVRD for remainder of flight as returning to NORM would reproduce the TERRAIN WARNING. Notified dispatch of ADS-B OUT; TERR POS; GPS Jamming; DME-DME degradation and false PULL UP messages and EFB discrepancies along with difficulty on VHF with Egyptian controllers via free text message.Flying in close proximity to a known active war zone seemed to be a source of the interference/spoofing/jamming. The corruption of the GPWS database; the uncommanded turn of the aircraft seeming to indicate a map shift and most importantly the false TERRAIN PULL UP Warnings are not detailed in either company briefings. It would seem that either a more comprehensive capability has been achieved to dive deeper into an aircraft's system via jamming/spoofing or software changes since these guides were published have inadvertently created greater vulnerabilities.Greater lateral separation from known active war zones should be a priority. Given the possible ATC; governmental and political considerations that may make this difficult on short notice; locking out of release(s) should be mandatory until a verbal brief to the Captain is accomplished by either Chief Pilot or Dispatch with latest known intelligence/feedback is accomplished. We were fortunate that these events occurred in day/VMC conditions and were single event items. Had this been at night or in weather or had two or three of these indications occurred simultaneously a much more serious outcome could have happened.