javascript - How to recognize a previous user/spammer without cookies? -

i admin on chatting website , lot of abusers everyday, disrupting regular chat flow. keep banning ips , keep changing them ip-changer software , proxies. additionally, enter using "private browsing sessions" (this our deduction, because cookie-marking them doesn't work).

is there means recognize presence before start nefarious activities?

we have javascript (no ajax though) , php5 @ our disposal. have read in detail "browser fingerprinting". sounds promising, incorporates lot of values obtained solely through ajax (screen res, installed fonts etc).

i stick standard php5 as possible, , non-ajax javascript may employed if necessary.

userbase:

• 90% windows-based
  • nearly 80% windows 7 on portable devices
  • 10% on xp
  • 10% on windows 8
• 10% mac os.

obviously should implement user registration if isn't there already, email address confirmation or oauth validation. pure php, far can see, there little else can do. can try putting data localstorage (will require little js), not knows yet might catch low-swinging trolls way. can make people don't have identifying cookies ('newbies') have wait while in order join chat. way established users won't suffer.

must say, i'm confused saying don't have ajax 'at disposal'. ajax except js sends data php (or other) script on server? ajax can auto-ban users get, example, 5 flags other chatters. without handicapped, because once user starts chat have no other way of knowing until visit page on site, chat application seems anyway less usual.