Abandoned? Alternatives?

It really depends on what exactly in Troll you're trying to duplicate. All these have relevant functionality to what Troll does, but are completely separate paths to doing it.

http://drupal.org/project/httpbl
http://drupal.org/project/misery
http://drupal.org/project/mollom
http://drupal.org/project/phpids
http://drupal.org/project/spambot

Great list. My contribution to the alternatives:
http://drupal.org/project/ip_ranges

Thanks, good little thread to replace Troll!

Here some quick basic research additions - I may have missed some things - please add:

• http://drupal.org/project/httpbl - D5, D6 & D7 - Reported installs: 651 sites currently report using this module. - Implementation of http:BL for Drupal. http:BL can prevent email address harvesters and comment spammers from visiting your site by using a centralized DNS blacklist. It requires a free Project Honey Pot membership. This module provides efficient blacklist lookups and blocks malicious visitors effectively. http:BL has been adopted for use to enhance protection on Drupal.org.
• http://drupal.org/project/misery - D6 & D7 - Reported installs: 125 sites currently report using this module. - Misery is a module designed to make life difficult for certain users.
  It can be used:
  • As an alternative to banning or deleting users from a community.
  • As a means by which to punish members of your website.
  • To delight in the suffering of others.

  I am not quite sure this is the right way in general. "Be straight or don't bother us" might be better, the world is full enough of 'misery' - no need to add to.

• http://drupal.org/project/mollom - http://mollom.com/how-mollom-works - is a third party service Reported installs: 43106 sites currently report using this module. - free basic service - premium service from €30/mths
• http://drupal.org/project/phpids - This module is currently being rewritten - See main issue for current state: #1726730: PHPIDS integration rewrite Sprint tasks
• http://drupal.org/project/spambot - D6 & D7 - Reported installs: 1654 sites currently report using this module. Third party service -(www.stopforumspam.com)- not-for-profit - donations welcome - I am sure ...
• http://drupal.org/project/ip_ranges - only D7 upwards - Reported installs: 263 sites currently report using this module.
• ------------ some more ------------------
• http://drupal.org/project/goaway - D6 & D7 - GoAway is a dirt-simple, light-weight "Ban By IP" module. It works by redirecting offending anonymous users to a local page or remote URL specified by the admin. - Reported installs: 287 sites currently report using this module.

Might be useful to summarize this for D7 and put it up on the project page.