what's the density of open port 21s on the planet though? trying to estimate the traffic resulting against the two target /21s.
Your dump only has 2 ip's in it though, on your /19 so not representative. My dump is 500 synacks returned in 14 seconds to 32 ips in a /22. This would give 128M ftp responders across the whole /0 (modulo actual space in use, etc, so call it 32M responders?). (It's also a short timespan for a dump as well.) Syn-ack seems to be a 58 byte packet (?ish). 32 * 10^6 * 500/14 * 58*8 / 10^9 = 530 Gbps even if im off by 4 in density of ftp sites on the internet despite my already reducing it by 4, we're talking ~100+ Gbps. /kc On Tue, Nov 01, 2016 at 03:59:49PM -0600, Selphie Keller said: >Yeah it is an odd ball attack for sure, here is a 5000 packet sample of >what I was seeing in connection to this attack >https://mystagic.io/80to21.pcap , don't think it's the entire /0 for ftp >port as I am not seeing it on many other subnets, which is why I am >thinking someone did a pre-scan before conducting this wacky attack, >otherwise, I would have likely seen other port 21's seeing activity, but so >far any IP that didn't have 21 as an actual service isn't seeing the syn >packets. This could be unique to my location, others observing this attack >may be able to chime in and report what they are seeing if they seen 80 src >syn to port 21 where 21 isn't an actual ftp running. Yeah this is pretty >easy to filter. > >On 1 November 2016 at 13:48, Ken Chase <m...@sizone.org> wrote: > >> Not sure why reflected RSTs are the goal here, they're not much of an >> amplification >> to the original syn size. Additionally causing a mild dos of my clients' >> stuff >> when it begins throttling # of connections, ie noticeable. (not that i >> want to >> help scriptkids improve their attacks...). Im guessing port 80 was chosen >> for improved >> fw piercing. >> >> Sure is widespread though, 5 clients on very different networks all seeing >> similar >> saturation. Someone has a nice complete prescanned list of open ftps for >> the >> entire internet out there (or are they just saturating the whole /0?) >> >> Easy to filter though: >> >> tcp and src port 80 and src net '(141.138.128.0/21 or 95.131.184.0/21)' >> and dst port 21 >> >> Adapt for your fw rules of choice. >> >> /kc >> >> >> On Tue, Nov 01, 2016 at 07:39:40PM +0000, Van Dyk, Donovan said: >> >I think Ken has nailed it. I think the source addresses are spoofed so >> you reflect the connection (tcp syn ack) to those source addresses. Get >> enough of those connections and the server is dead. >> > >> >Since your port 21 is open >> > >> >telnet 109.72.248.114 21 >> >Trying 109.72.248.114... >> >Connected to 109.72.248.114. >> >Escape character is '^]'. >> > >> >Your address was probably scanned and saw it could be used in the >> attack. >> > >> >Regards >> >-- >> >Donovan Van Dyk >> > >> >SOC Network Engineer >> > >> >Office: +1.954.620.6002 x911 >> > >> >Fort Lauderdale, FL USA >> > >> > >> > >> > >> >The information contained in this electronic mail transmission and its >> attachments may be privileged and confidential and protected from >> disclosure. If the reader of this message is not the intended recipient (or >> an individual responsible for delivery of the message to such person), you >> are strictly prohibited from copying, disseminating or distributing this >> communication. If you have received this communication in error, please >> notify the sender immediately and destroy all electronic, paper or other >> versions. >> > >> > >> >On 11/1/16, 3:29 PM, "Ken Chase" <m...@sizone.org> wrote: >> > >> > seeing an awful lot of port 80 hitting port 21. (Why would port 80 >> > ever be used as source?). Also saw a buncha cpanel "FAILED: FTP" >> alerts flickering >> > on and off as the service throttled itself at a couple client sites >> I manage. >> > >> > I see 540 unique source IPs hitting 32 destinations on my network >> in just 1000 >> > packets dumped on one router. >> > >> > All from multiple sequential registered /24s in whois, but all from >> one >> > management company: >> > >> > 141.138.128.0/21 and 95.131.184.0/21 >> > >> > role: William Hill Network Services >> > abuse-mailbox: networkservi...@williamhill.co.uk >> > address: Infrastructure Services 2 City Walk Sweet Street >> Leeds LS11 9AR >> > >> > AS49061 >> > >> > course, synfloods can be spoofed... perhaps they're hoping for a >> retaliation >> > against WHNS. >> > >> > /kc >> > >> > On Tue, Nov 01, 2016 at 09:44:23PM +0300, Oleg A. Arkhangelsky said: >> > >Hello, >> > > >> > >A couple of cuts from tcpdump output: >> > > >> > >21:31:54.995170 IP 141.138.131.115.80 > 109.72.248.114.21: Flags >> [S], seq 1376379765, win 8192, length 0 >> > >21:31:55.231925 IP 194.73.173.154.80 > 109.72.241.198.21: Flags >> [S], seq 2254756684, win 8192, length 0 >> > >21:27:50.413927 IP 95.131.188.179.80 > 109.72.248.114.21: Flags >> [S], seq 3619475318, win 8192, length 0 >> > >21:27:50.477014 IP 95.131.191.77.80 > 109.72.248.114.21: Flags >> [S], seq 2412690982, win 8192, length 0 >> > > >> > >Does anyone seeing this right now (18:31 UTC)? I see this traffic >> > >on at least two completely independent ISPs near Moscow. The >> > >rate is about a few dozen PPS hitting all BGP-announced networks. >> > > >> > >--?? >> > >wbr, Oleg. >> > > >> > >"Anarchy is about taking complete responsibility for yourself." >> > >?? ?? ?? Alan Moore. >> > -- Ken Chase - m...@sizone.org Guelph Canada