MikroTik

Folks,
Can the routerOS currently do the above? I.e. If i have blocked the keyword "porn", anyone who uses the any search engine, the RouterOs will perform "man in the middle" operations and block the search.

Regards,
DataNav

Not on https or other encrypted connections, as RouterOS doesn't do the actual MITM in the security-related meaning of the term; to some extent, with a high probability of false positives, you can do that on plaintext protocols like http using /ip firewall layer7-protocol.

You can not do that with Mikrotik router since HTTPS packet are encrypted.

But with a corporate network that controlling the PC, you can use products like Forcepoint (https://www.forcepoint.com/)
When you do surfing it will replace the HTTPS certificates and Forcepont will surf on behalf of the clients.
Our company do use system like this so my search at work are restricted.