What was found
FLT#1621, LHR-BOS. (ETOPS) 'WHILE DESCENDING THRU 8000' WITH THRUST AT IDLE A STRONG DIRTY SOCK SMELL APPEARED. ODOR WAS STRONG ENOUGH IN CABIN FOR IN-FLIGHT TO CALL TO REPORT IOT. ODOR THROUGHOUT OUT CABIN AND COCK PIT ODOR PERSISTED TO THE GATE NO TROUBLESHOOTING ATTEMPTED; REF DEFECT 3727229 (ACCOMPLISHED TSM 05-50-00-810-831-A. C/W INFO NOTICE 2017-T015J AND SUBTASK TSM 05-50-00-810-085-D. APU OVERSERVICED. REMOVED OIL FROM APU. DECONTAMINATION ACCOMPLISHED.) FOR RESOLUTION, ALSO REPLACED OZONE FILTER #2 PER AMM 21-51-41.- A/C GOOD FOR SERVICE.'