Why did Google start asking for captcha?

Question

Google

There are about 20 computers at work, the server is on debian linux, the rest with win xp with the latest updates. The Internet goes through ADSL, IP is white and static. The modem is plugged into a separate computer with traffic inspector, the computer is clean, there are no viruses.
When trying to find something on Google, a message began to appear:
"We have registered suspicious traffic coming from your network. Using this page, we will be able to determine that it is you who are sending requests, and not a robot."
And you need to enter a captcha. And this message gets out, even when viewed from the phone. This has never happened before.
How can this be fixed? In general, it is not clear which way to dig.

Answer 1

In general, it is not clear which way to dig.

Toward Yandex?

Answer 2

Write to google.
And check if you really have suspicious traffic that is shitting requests?
"the computer is clean there are no viruses" - all 20 do not?

Answer 3

This situation occurs when someone from your IP drives a script that parses search results pages (scraping). You should dig in this direction, i.e. ask them to randomize the latency and/or user agent values.

Answer 4

For me, it became an IPv6 solution, at first they were asked to enter a captcha, then a temporary ban on requests followed.