I don't think this is limited to brightcloud. I have tried at least 3 different antivirus programs and they all label sisyphusion.tk as a malware site. For example, here is Trend Micro: http://global.sitesafety.trendmicro.com/

I could tell from their malware-ish user-interface for their virusscanner that they sucked :) this is what they explain

Is it safe?
Dangerous: The latest tests indicate that this URL contains malicious software or phishing.
How would you categorize this URL?
Spam: Sites whose addresses have been found in spam messages
Disease Vector: Sites that directly or indirectly facilitate the distribution of malicious software or source code

The criteria is asinine -- millions of spammers since the dawn of spam use "at" google "at" nbc "at" any legitimate business or website in their spam to lend an air of legitimacy

Then you have the weasel-words "directly or indirectly", "facilitate"... weak

this says safe, this says safe

I couldn't find any more websites update: searching for "at"..... I found sisyphusion.tk safe website ? Check it now which not only says its safe, it also says TrendMicro Clean NOT FOUND that means its safe, its not on the trendmicro blacklist -- among 26 others (27 total) -- thats a contradiction