Ddos

A few weeks back an Indian ISP contacted me via a contact form on my blog. That ISP has been struggling with a targetted DDoS attack. For the reason of privacy as well as the stability of their network, I will not put their name or AS number. The attack on that ISP was much higher than their bandwidth levels. Their upstream did not really share the volume of attack but I could tell from the screenshots they shared was that it was distributed volumetric attack choking their upstream bandwidth. I suggested that ISP get the blackholing option from his upstream (preferred way) or buy a cheap server/VM somewhere outside India with BGP (and BGP blackholing) and manually blackhole traffic when the attack comes. They were able to get blackholing enabled from their upstream and it did work. They started blackholing traffic and it helped to manually drop traffic going towards the IPs which were being attacked. It’s important to have BGP blackholing because it helps a network to signal upstream ISP about the pools which are under attack and to drop traffic towards them. ISPs further signal the same to their upstream and larger networks typically drop that traffic on all their edge routers i.e closer to the entry fo attack.   Next, the problem which hit that ISP was that it was a pain to manually find IPs which were under attack and quickly drop them. I suggested them to try fastnetmon. I heard of fastnetmon from the presentation of Job Snijders at NLNOG (slides here & video here). Fastnetmon is developed and maintained by Pavel Odintsov (who works at Cloudflare AS13335).