▁largest ▁bre aches ▁of ▁government ▁data ▁in ▁the ▁history ▁of ▁the ▁United ▁States , ▁in ▁which ▁an ▁estimated ▁ 2 1 . 5 ▁million ▁records ▁were ▁st olen . ▁Information ▁target ed ▁in ▁the ▁bre ach ▁included ▁personally ▁ident ifiable ▁information ▁such ▁as ▁Social ▁Security ▁numbers , ▁as ▁well ▁as ▁names , ▁dates ▁and ▁places ▁of ▁birth , ▁and ▁addresses , ▁and ▁likely ▁involved ▁the ft ▁of ▁detailed ▁background ▁security - clear ance - related ▁background ▁information . ▁ ▁In ▁June ▁ 2 0 1 5 , ▁the ▁US ▁Department ▁of ▁Def ense ▁( Do D ) ▁included ▁a ▁chapter ▁dedicated ▁to ▁cy ber ▁war fare ▁in ▁the ▁Do D ▁Law ▁of ▁War ▁Man ual . ▁See ▁Cy ber ▁War fare ▁section ▁on ▁p .   9 9 4 . ▁ ▁In ▁ 2 0 1 6 ▁Cy ber ▁Command ▁mounted ▁computer - network ▁attacks ▁on ▁IS IS ▁under ▁Operation ▁G low ing ▁Sym phony ▁with ▁the ▁intent ▁to ▁dis rupt ▁internal ▁communication , ▁manipulate ▁data , ▁and ▁und erm ine ▁confidence ▁in ▁the ▁group ' s ▁security . ▁A ▁particular ▁emphas is ▁was ▁placed ▁on ▁lock ing ▁key ▁figures ▁out ▁of ▁their ▁accounts , ▁deleting ▁files ▁of ▁propag anda , ▁and ▁making ▁it ▁all ▁look ▁like ▁general ▁IT ▁trouble ▁instead ▁of ▁an ▁intent ional ▁attack . ▁This ▁operation ▁prompt ed ▁an ▁internal ▁debate ▁in ▁the ▁American ▁government ▁about ▁whether ▁or ▁not ▁to ▁alert ▁their ▁al lies ▁that ▁they ▁would ▁be ▁attack ing ▁servers ▁located ▁within ▁other ▁countries . ▁In ▁March ▁ 2