How to find out where the transitions to the site come from?

Question

Traffic analysis

Hello everyone, the last few days the site has been receiving incomprehensible traffic, + - 500 uniques per day, on the same page, but in the metric the entry points look like this:
https:// site/page1/?sub1=cwmdm5d165faf15897102549331
https:/ /site/page1/?sub1=fpzje5d1a37c49ec2c161787494
https:// site/page1/?sub1=fxakk5d1741612e444775950338
https://site/page1/?sub1=gaufe5d166583b3938354801008
https:// site/page1/?sub14=zhtsh5d18
etc. , the traffic sources indicate referrals from away.vk.com and direct visits (approximately 30-40% from VK, the rest are direct visits). At the same time, all visitors come from Android and iOS mobile devices, mainly from the Russian Federation, the behavior on the site is different, they look like live ones, browsers are different.
Three questions. Are there options to find out the source of the transition, do I need to do something about it, and if so, how and what?