There is some nice research regarding systems "abusable" for reflection by tcp port and the amplification factor depending on the OS: http://www.christian-rossow.de/publications/tcpamplification-woot2014.pdf
And in more detail: https://www.usenix.org/system/files/conference/usenixsecurity14/sec14-paper- kuhrer.pdf Best regards, Chris On Tue, Nov 1, 2016 at 11:21 PM, Ken Chase <m...@sizone.org> wrote: > 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 >