Hi:
the zabbix version I use is 4.0.x and 5.0.x LTS.

I was suffered by huge network sessions caused by passive proxy. with tcpdump, we can see zabbix-server create a new tcp port every second for every passive proxy.
at first, I thought there was something wrong with the parameter "ProxyDataFrequency", so I create issue ZBX-18455 but got no further response.

I checked the source code, and found that by design zabbix-server use three parameters to judge the frequency for contacting passive proxy. we can change "ProxyConfigFrequency" and "ProxyDataFrequency". but by default the third parameter "ZBX_TASK_UPDATE_FREQUENCY" is one second and can not be changed. the "ZBX_TASK_UPDATE_FREQUENCY" parameter is only used for proxy, but I don't why it is necessary. I replaced the two "ZBX_TASK_UPDATE_FREQUENCY" with "CONFIG_PROXYDATA_FREQUENCY" at "src/libs/zbxdbcache/dbconfig.c",then 90% of sessions gone with parameter "ProxyDataFrequency=60".

I don't know what's the side effect although it seems working fine. I hope that zabbix proxy network design can be fixed. it is unpleasant for firewall to saw huge useless connections.