我有一个在没有 iptables 配置的情况下运行绑定的 dns 服务器。使用 nmap 运行一些扫描仪，我发现在一些高时刻端口没有打开但很快关闭，并保持在该循环中。当我以 root 身份行走时，这些端口不会随时出现。
这是 nmap 的输出：
Host is up (0.00022s latency).
Scanned at 2016-09-10 01:04:48 UTC for 0s
Not shown: 64996 closed ports
PORT STATE SERVICE
22/tcp open ssh
53/tcp open domain
111/tcp open rpcbind
52347/tcp open unknown
过了一会儿……
Host is up (0.00022s latency).
Scanned at 2016-09-10 01:04:49 UTC for 1s
Not shown: 64994 closed ports
PORT STATE SERVICE
22/tcp open ssh
53/tcp open domain
111/tcp open rpcbind
38248/tcp open unknown
52347/tcp open unknown
55806/tcp open unknown
netstat -ltnp 的输出
Conexões Internet Ativas (sem os servidores)
Proto Recv-Q Send-Q Endereço Local Endereço Remoto Estado PID/Program name
tcp 0 0 127.0.0.1:953 0.0.0.0:* OUÇA 7209/named
tcp 0 0 0.0.0.0:52347 0.0.0.0:* OUÇA 902/rpc.statd
tcp 0 0 0.0.0.0:111 0.0.0.0:* OUÇA 888/rpcbind
tcp 0 0 XXX.XX.XX.X:53 0.0.0.0:* OUÇA 7209/named
tcp 0 0 XXX.XXX.XX.X:53 0.0.0.0:* OUÇA 7209/named
tcp 0 0 127.0.0.1:53 0.0.0.0:* OUÇA 7209/named
tcp 0 0 0.0.0.0:22 0.0.0.0:* OUÇA 935/sshd
tcp 0 0 127.0.0.1:631 0.0.0.0:* OUÇA 1258/cupsd
tcp6 0 0 :::48323 :::* OUÇA 902/rpc.statd
tcp6 0 0 :::111 :::* OUÇA 888/rpcbind
tcp6 0 0 :::22 :::* OUÇA 935/sshd
tcp6 0 0 ::1:631 :::* OUÇA 1258/cupsd
我的系统是Linux lDebian13 3.16.0-4-amd64 #1 SMP Debian 3.16.36-1+deb8u1 (2016-09-03) x86_64 GNU/Linux
这些端口是什么？会bug吗？是后门吗？我怎样才能从他们那里得到信息？