Available as a Facebook app (free for personal use; business versions range from $299 to $7,999 per year), Defensio is designed to keep your Facebook pages free of unwanted and potentially harmful content. It's easy enough to use, but is somewhat hamstrung by Facebook's limiting APIs.

You can activate Defensio by clicking its Facebook page and granting it permission to access your Facebook account. You can have it protect personal Facebook profiles or Facebook pages (such as those set up for a business or other activity) from profanity, spam, and potentially malicious content, such as viruses and phishing scams.

The problem is that Defensio's ability to protect a personal profile is limited by Facebook's API, which does not allow third-party apps to remove content from a user's profile: The user must delete the content him- or herself. That means that every bit of risky content and profanity--from relatively mild swears like "hell" to more offensive curses, like the f- word--appears on your profile. Defensio simply alerts you (at an e-mail address you supply) that suspect content, such as "possible profanity" has been posted. Unfortunately, Defensio's e-mail alerts (which you can turn off) always arrived a few minutes after the Facebook message telling me that a friend had posted on my wall. Because I had Facebook's own alerts enabled, that meant Defensio's alerts were only telling me what I already knew.

Another issue: Defensio's default profanity feature isn't enabled by, well, default. I had to turn it on manually. Before I did so, the app didn't alert me to any profanity at all. Once the default feature was enabled, the app proved fairly adept at picking up suspect profanity, catching most of the swears sent my way, with no false positives. Unfortunately, though, it missed several posts, including some with the same curse words it had previously identified. Results with porn links were similarly mixed: It failed to notify me of one link to a porn site that had been posted to my wall, even though the link's description contained the phrase "naked girls." It did, however, flag a posted link to a more well-known porn site with a more obvious name.

When Defensio does catch posts containing suspected profanity, spam, or malicious content, they're listed in its "Comment Moderation" section. You're given two options: "Delete" or "Not Spam." Opting for "Not Spam" simply removes the comment from Defensio's list. And while you might think that selecting "Delete" would delete the post, you'd be wrong. Instead, it generates a pop-up message telling you that due to Facebook limitations, you must manually delete the post.