The attempts on my PBX are increasing and increasing and from the mailing lists I get a similar picture. The big issue is that many, if not most, ISPs don't react to complaints. For that reason I will, starting now, publish the top 20 of attacking IPs here on my website, including whois links, so people can see, how big the problem is and what providers do. I'll additionally start compiling a blacklist of the "worst" networks, so admins can put those addresses in their firewall rulesets.