[Plugin Akismet] Not catching spam

For the last few iterations of Akismet and for about 3-4 months, I’ve noticed the plugin simply isn’t catching spam. The comments are marked in history as “Cleared by Akismet” but the comments are clearly, evidently spam. The tracking stats on my account are completely inaccurate, and I often wake up to 12-15 spam comments. Is there a fix here or does the plugin simply not work well any longer?