Twitter said the site's blackout was caused by a "denial-of-service attack, " which likely means a hacker used a number of infected computers to send enough automated requests to the site to overwhelm it.
One of the most startling was the attack on the global intelligence firm Stratfor over Christmas, for which members of the loose-knit hacker group Anonymous claimed responsibility.
The most common passwords on Christian blogging site Faithwriters included words like jesuschrist, heaven, christ, and blessed, all easy enough to guess for a hacker to guess or even easier to find with a dictionary attack that cycles through millions of word variants.
But patching the vulnerabilities used for mass infections of sites, which often use automated tools to spread malware among thousands of targets, is very different from patching every vulnerability a hacker could possibly use for a targeted attack on a single victim site.