freelistfool - 7:48 pm on Mar 9, 2012 (gmt 0)
I had something similar happen to one of our sites. However, my traffic comes from several different browsers (mostly Firefox) so it might not be the same issue...but I'm posting our experience in hope that it helps.
On 2/21/2012 we noticed a spike in direct traffic with the following characteristics.
1. Hitting only the home page
2. Accounts for more than 90% of the traffic to the page
3. Has a high bounce rate (over 75%)
4. Coming from a large number of different IPs
5. Coming from several geographic locations
6. Used several different browsers
Once we isolated what a bad hit looked like we traced several of their IP addresses in our logs to see how many times a single IP was hitting the site. During this process we found a very small number of hits from those IPs with a referrer. The first hit to our site from that referrer was on 12/9/2011. The referral and direct hits started out very small but the direct traffic grew exponentially (doubling every two weeks).
We blocked the offending referrer and it cut the direct traffic in half within about 24 hours. During the process of reverse lookups and blocking IP addresses on the direct traffic we found that the majority of hits were from the same country (Bangladesh in our case) and almost all hits with a referrer were from the same country. So we just blocked all traffic from Bangladesh. Within 72 hours our traffic was back to normal and the direct hits from all other geographic locations was back to normal too. As of today, the attempts to hit our site from the bad IP addresses has dropped from several a minute to only a handful a day.
Now we're hoping it doesn't pop up from another country or referrer. Hope this helps.