Distributed　denial　of　service　(DDoS)　attacks　have　become　a　hidden　danger　in　the　development　of　the　internet　of　vehicles　(IoV).　DDoS　attacks　for　TCP　protocol　are　studied　to　improve　the　information　security　environment　of　IoV.　For　the　distribution　characteristics　of　DDoS　attacks,　an　information　sharing　and　collaborative　detection　mechanism　based　on　multi-agent　is　proposed.　Considering　the　relationship　between　the　features　of　adjacent　moments　in　the　TCP　communication,　the　DDoS　detection　model　based　on　hidden　Markov　model　is　built,　and　the　Viterbi　algorithm　is　improved　for　the　problem　of　the　false　alarm　in　the　observation　sequence.　The　optimal　communication　strategy　among　agents　is　determined　by　deep　reinforcement　learning,　and　fusion　algorithm　is　designed　to　improve　the　current　strategy　of　agents.　Three　groups　of　comparative　experiments　are　designed　and　analyzed.　The　simulation　results　show　that　proposed　algorithms　are　effective.　©　2022　John　Wiley　&　Sons,　Ltd.