What’s also unclear is whether the URL-filtering extends to the many third-party apps people use to access Twitter. (I use TweetDeck, for example, and it appeared that my attempt to tweet a malicious link was blocked—though there was no notification as to why). I’ve put in an info request, and will update accordingly.

Improved security is a must if Twitter ever plans to make money by charging enterprise users; it will also go a long way toward getting brands more comfortable about spending money directly on Twitter-based ads (if the startup decides it wants to try to make money that way).

The new feature has surfaced (coincidentally) just a day after the annual Defcon hacker conference. Twitter was a resident on the Defcon “Wall of Sheep,” which shows a stream of passwords and login info from people that have unwittingly exposed their data over various networks (per Forbes); the startup got a better security grade this year than last year—but hackers still said Twitter could be doing more to protect its users.