weird weblog entries

I see stuff like this in my web server logs:

70.18.8.39 - - [01/Oct/2005:13:07:43 -0700] "GET /level/16/exec/-///pwd HTTP/1.0" 404 219 "-" "-"

Lines like this started showing up less than a week ago. Anyone know what it could be? A new worm, something?

Update: Someone's scanning for a misconfigured Cisco box.