New SMTP DoS ?

[katmai]

Hey guys, i just came up with this thing happening on one of my servers. I have never seen it before. The ips seem to be spoofed, since i took a tcpdump and some of the ips that appear in the exim_mainlog, don't appear in the dump, however i am not sure how to go about this.

It doesn't really do anything, the server doesn't go down, but i just don't like shady stuff happening at all.

Anybody seen this before, and does anyone have any idea how to get rid of this junk?

2013-09-27 06:48:16 SMTP syntax error in 
"/\275\377z\005:\233\vH8\032\f\364K<~\3104\030\r\030\231\260\rW\227\322\177\230\225\256\016\347\371F\017\007\364\252\020\346 \002\210e\360\250\021\367X\\[email protected]\213\364\021\241\307\377\2037\317\225\204\007\270q\023\266\313\223\205\237\311\022\206\313\262\221\206\033\027\207\025 Z\025\006\026\233\023\205\026?\016\351\027\035\200\200\227\233p?\031S\204*\225\355p\274\212<\325\261\031|\3230\032\275A\255\232\376\317.\033Th\340\033 1/+\035\316\340\302\234\300\221B\036\361!n\232\362\[email protected]\037f\037l\233-\244p\237nb\357\237\257\360p \004\357\357 2\355n!\177Q\007"\300O\206"\021N\005#BL\204#\203J\003$\321\256\233$\022\255\032%S\253\231%\241\0172&\342}\256\246\360 \323\230\002VY\244+\377\330\244\027m\306(4\333B\251\221f\251*\315\336\354\246\334\214s\247\271X\354\247J\261j\250\301T\352\250E(\326-V)p-\227'\357-\330%n.&\212\006/g\210\205/\250\206\0040\351\204\20307\351\0331x\347\2321\271\345\0312\007J\2622HH13\211F\2603\312D/4\030Y\305\264Y\247F5\232\245\3055\333\243D6)\b\3356j\006\7[\001\3008\354\002Z8,\001\3318\223S\002\266\274\361\201\266\374ao:8\356\177\267\261\232\027\270\234\255\226\270>\276i=]%\035=\264#\235=\336!\033>\037 \232>m\2042?\256\202\261?\357\[email protected]\177\[email protected]~\343GA\277\341\306A?\340EBA\336\304B\202\334CC\[email protected]\334C\021?[DR=\332D\223;YE\341\237\361E"\236pFc\234\357F\261?\210G\362\376\006H3\375\205H\201a\036I\302_\235I\003^\034JD\\233J\205Z\032K\323\276\262K\024\2751LU\ 273\260L\226\271/M\344\035\310M%\034GNf\032\306N\247\030EO\365|\335On{\P\232y\333P\333wZQ\346\330.RG\332qR\210\330\360R`\017" H=[109.86.30.113]:1365 I=[MY_IP]:25 NULL character(s) present (shown as '?')
2013-09-27 06:48:16 SMTP syntax error in "\1770\026"c\306\361n\251;\020B\204\333Z\300Y0\031q\301\323\204\v\030ZTHo\340#\205\300\033g\364\260\220KS\233\323\207Z\222\001\270g\3064ksws\331}_\265 `\203V\343\220\220\375g\376\352\001\357\341\336\274\205N\316\203\007\257\303<\225M\266\177*\202\245:\301\356\224\304=\314\213B\317\265|\300`\237m{\367 \v]\005t\351S \373\314G\r\202\260;\020]U+\314\237?\037\223!a\024\213\275P\002\311\377xR\315\206\F\016\023\3038\311\251/(O;\031\031\016\275y\016\341)\316 S\320\303\364?sn\341\036\331\007\336\245\236\240\323\335\366W\301[\210A\262\331\031+\243c\226\b\232\337\036$\216\234\276^zv\177tq\355\274\234f\234h\025P\032\372\[email protected]\034x\0248k\370<-\335\2362\030[0\034 \234\274\202\373&9`\362[\332\322\336Sv\302\314\335\362\237\303*j\372\273\331\025s\245\vm\247\357\322\356\007\345Z\334\211\263\252\\352\250\242\370\331\226\246\177\275\2120\37 4\232\201\337\247\023k 4z]\234\274\225Q\2567;H \33603\333t\235"\337\373\200\026\262h\325\021$\017\313\374Y\260=\351\343,\033\340\263\342*\332(@e\306\254\346Z\261\202\272){\030"\373w\323\270gg\327?K[a\274(R\3538\006I\330\035\2615\022X\216,\256\3359 \276O\021\0321*\266 \225\002\325>\325\267\3448\364\313\3649\255Y\223,\022\320\265$\317F\020\035Y\303%\024\037m\005u\236\3267\372\337b\236\354\357\304sf\367l\346\325,\001\ r)h\177\3053\302\353\200\267B}j\250\215\364i\022\332k\037\231|\371\211\213\017{\352\200x<\250\344i~\253kx\376(\3347\310\037O\373\223\202\264v\244\324\ 257F\033\2260\270\267\036\226\241C\205\210" H=[122.161.166.247]:26584 I=[MY_IP]:25 NULL character(s) present (shown as '?')
2013-09-27 06:48:16 SMTP syntax error in "\300ny\242'\233\004\036\271\204\365\273\345\214\2248D\\224\317\316E\002\003b\254wA\371\033\350\252Y\b\327f\360\317Tub\247N\266\336\v\301XA\323C\241\3 72a6\004L\033-\336\240~\234\333?S\034IcM\210%.\b\r\037Cy}"\360\277wo\227\035p\177\031\367\351N\260c\331\032\b\254\332\340\211\f\320^\033\366\3005\235V\266\370 \253\261\263\240\027\241I\b\351\235\307\231\322\216\024\021-\207U\235\223y\242\004\354\3612\363\365U\237dJ\341G\311\206\326LD`\315\231\315G\301;&)9}C\0070\244Pe\241Zk]\[email protected]\rzY\022\001\300:\331\177\016\317Ao\346;\226j_\315\177[o?WU\355\[email protected]\2038\022C\001\312\3733\310K\)R\3109 %5\216\033\257\261k\022v3\314\007\364\304\265\370\3071" H=[122.161.166.247]:26584 I=[MY_IP]:25 unrecognized command
2013-09-27 06:48:16 SMTP syntax error in "\364\024i_lU5\313\336\323\306\264\317\3438\214\311\252\272\354\276(L\326\257\247\375\255)\312m\201#\331\337X\035E\345\253\312{j\306\243Z\242< \340\032k]YH\2046QB\236\017I*\037rh\022\270I\025\350I'\017\310\337\001\343\242\363\335=s\001\275\005c!\223\315RAi\255\030IK\276\370\337%\f\336\371\376\324\315\0 31\325\361\230\244\265\002y;\220\326SOl\333H\[email protected]\370\023}! \364\023\374&\277\236\334\261\251;\264\vzI\223\034Z\340m-:wH\246\245\243\325={4\263\227KB\222\3450\kp\033\371B\215\346\203#\236\306\032\376f\266:\324\264\233T\255\321f\337\215\326[\202b0,\220A5!3\026 \374F\362\032\334\335\314\254\254\353\253_\234\v\202\366q\234_\304NK:\3651\312\024\205\034g\354\336\311\373D\016\320\246\244}\3431}>\247\310S\261z\324 \260\304Wm\r4D" H=[122.161.166.247]:26584 I=[MY_IP]:25 unrecognized command
2013-09-27 06:48:16 no host name found for IP address 117.203.178.103
2013-09-27 06:48:16 SMTP syntax error in "\372\310\353\351\177C\300\362\234\215\311\372\2118i\004O\261\274\rI\302u\027\253\003\372!\245\024\263+k\215\0065\242\243B=\262\2072E\351\235nM\371\20 1^Uc8\204]M\342\243ej,\255m#?\347v3#\327~Pm\340\206\207\203\034\217\034\317(\227\301\027/\237\336a8\247s\316\214\257\030\366J\267(\332:\277E$D\307U\b4\317rR=\327\2026-\337G\3059\347\267d&\357\314\256/\367\366^R\377S\253\246\007#\215K\017\332\305\322\027\221\271\303\037\2277\232'\276\347\274/\016\316\3677\363\025\266?s\373\250G\350F\372O\030$?Y=\210\272\326UV\252\336t\240\241o\202\204\221w\237\316\232\177\301\030\244\207\365\022\246\006\35 3F\235\227\371*\237\0261A\311\247\305\214\325\257]o\302\267\266C)\304\306'\031\314\360\327;\324?\274+\334ClN\344-\352$\354W\232G\364g~7\374\221.Z\004q\025\225\f\276\S\0249BC\034\353\212L$\373n<,\030\271E4Bih<RMXD|\375zL\367|TT\251+t\\271\017dd\343\277\206l\005\24 4vt\020\356\177| \332o\204=\034y\214Zf\202\224\321\237 \235\256\306\307\244\315\376N\255b(X\2659=I\275\226" H=[117.203.178.103]:1788 I=[MY_IP]:25 NULL character(s) present (shown as '?')
2013-09-27 06:48:16 SMTP syntax error in "\254\313\302\250L\324\2247$\334\036 \222\344p\333l\354RJ\327\364<\370\256\374\326\247\321\004?X?\r\246\001x\026k\217\037\037A\367\237(\2523\331\253\254\374\373\263\3348pA\334\034\355\307 D\341\357\302\036D\240[C\216^c\266\363\330\332h\274Wsz\240G{\006\371\361\366\234a#\215\273\253,\225\274)\250\016\331s\f\245\341\352\336\256\307]\022\272A\301\3717\202's\311\257\335\265\317\021 \230\331M\254\240R\370\315tZc\004Z\360\313*\270kOvBs0y\377z\037$\372\022\375h\200\034\323\305\303-\260\324^8A\3229\276&\b\333FE\321.\311S\331\201\305 \363\032[\275\fYbe\240{\351\032\332\273p7%#x\033\244\177\200,\241W\006xq\342\216\035\035Q\021\222\244^\235m\353\263\037\233U[*C \2031\370B\303\270\264\366\347\277V\020&\307" H=[117.203.178.103]:1788 I=[MY_IP]:25 NULL character(s) present (shown as '?')
2013-09-27 06:48:16 SMTP syntax error in "*d\316\262\335\210\325w\367\306\334\017\253\353\343\304\304)\353lxN\362!\222\214\371\326\253\312?\213\305\b\[email protected]\277D\217\302\r*\210N1\354\035\247(b&\0 24F?,\310\366\3044\211\0013\267\351UX\276\315\340\004I\367\210\324\314\357\226\370\323\332U7\333\305\336DgA\216\004o\355A)v\221\365M}\331j\237\207\250 P\020\217P\0045\226\370\267Y\235\240k~\244H\037\243\253\360\322\307\262\230\206\354\[email protected]:\021\301\350\3555\310\220\241Z\31785zV\340\b\244\335\210\274\ 310\3440p\355\353\330#\022\363\200\3276\372\330\207\274\002\320>\200\bw\362\244\0178\224Z\223\310\347\177\232|s,%\037\265\342\250\362\260\006\260Dy+\2 67\265o\353C.&\257I\354\331\324P}\215\370W%A\035_\332Z[f\202\016\200m*\302\244t\322u\311{z)\356\202"\335\022\212\312\2207\221rD\\230\032\370\200\237\302\253\245\246j_\312\255\022\023\357\264\272\306\023\27 4bz8\303" H=[117.203.178.103]:1788 I=[MY_IP]:25 NULL character(s) present (shown as '?')
2013-09-27 06:48:16 SMTP syntax error in ".]\312\262\341\201\321Z\225\246\330\002I\313\337\252\374\357\346R\260\024\356\372c9\365\242\027^\374J\313\202\003\362~\247" H=[117.203.178.103]:1788 I=[MY_IP]:25 unrecognized command
2013-09-27 06:48:16 SMTP call from [117.203.178.103]:1788 I=[MY_IP]:25 dropped: too many syntax or protocol errors (last command was ".]ʲ▒▒Z▒▒▒I▒ߪ▒▒▒R▒▒▒c9▒^▒J˂▒~▒")
2013-09-27 06:48:17 SMTP connection from [109.99.141.170]:3765 I=[MY_IP]:25 (TCP/IP connection count = 18)

 

[quizknows]

You can block the worst IPs with CSF but at this point there's no stopping it completely. I put some custom regex's for LFD in this thread.

http://forums.cpanel.net/f185/sustained-exim-attack-syntax-errors-mitigation-measures-338792.html

 

[katmai]

You can block the worst IPs with CSF but at this point there's no stopping it completely. I put some custom regex's for LFD in this thread.

http://forums.cpanel.net/f185/sustained-exim-attack-syntax-errors-mitigation-measures-338792.html

well i think most of the ip addresses are spoofed, because i ran some tcpdump, and then checked some ips from exim_mainlog, and they did not show up. it's hundreds of ips doing this. what worries me is that i might block some legit servers from accessing my box.

 

[cPanelMichael]

Hello

You may want to consult with your datacenter/NOC to see you can implement a firewall/DDoS device that can mitigate the DDoS or filter that specific traffic.

Thank you.

 

[quizknows]

No legitimate mail server would be sending this kind of traffic. The IPs will be correct, SMTP is a TCP connection, you can only spoof source of UDP packets such as DNS. Are you using only numeric IP addresses and not reverse DNS records?

Like michael said, you may want to contact your data center to see if they can help. Otherwise, best I know of is the custom LDF regex to block the worst offending IP addresses.