Angel is a simple yet useful tool to monitor the services on your network. Technically speaking, it's a Perl program that runs every 'n' minutes (usually fired from your cron) and calls different perl subprograms (referred to as "plugins" from now on) to do the actual testing. It will then generate an HTML table containing the status of your network.
Active Spam Killer (ASK) protects your email account against spam by confirming the sender's email address before actual delivery takes place. The confirmation happens by means of a "confirmation message" that is automatically sent to all "unknown" users. Once the sender replies to that message (a simple reply will do), future emails from that person will be delivered immediately. You can also specify (regexp) addresses to be immediately accepted, rejected (with a nastygram) or ignored. The package also includes a utility to scan your old mailboxes and generate a list of emails to be accepted automatically.
Webknock is a program that continuously scans Apache's "access" logfile and executes a configurable command when a certain URL sequence is detected. The IP address of the client can be passed to the command to be executed, allowing one to use iptables to open certain ports (usually, SSH) to certain hosts as soon as the correct URL sequence is activated. No changes to the Web server configuration are necessary.
Re: Challenge response considered harmful
> Response:: reply w/o modifications.
> Faults: Sends challenges to innocent
> third-parties as a result of
> spoofed ehaders.
This is not an ASK problem, but rather a weakness in the SMTP protocol. Take MTAs for example. They send bounces to the envelope address, which is very easy to forge. If a spammer starts sending millions of emails with a forged "envelope-from" containing your email, you will receive zillions of bounces in no time.
So, as you can see, programs that "blindly" reply to a forged address are been with us for a long time, including all MTAs, autoresponders, mailing-list managers and everything that talks SMTP. The problem has not been created by challenge-authentication agents.
ICQ Client Comparison
I depend heavily on ICQ to communicate with friends and family abroad. I currently use Licq on Linux (most of my friends use ICQ). I'd say I'm almost completely satisfied with it (the only big miss is a fully functional Gnome version and applet or at least a Gkrellm plugin).
Just to make sure Licq is still the best solution for me, I give other clients a try from time to time. I've posted the results of my "quest" at:
Of course, this just reflects my personal feelings and needs. Your mileage may vary.