New SMTP DoS ?

katmai

• September 29, 2013 09:10

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\\021@\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\215@\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\2000@0\177\257@~\343GA\277\341\306A?\340EBA\336\304B\202\334CC\320@\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$\216\234\276^zv\177tq\355\274\234f\234h\025P\032\372\376@\034x\0248k\370<-\335\2362\030[0\034 \234\274\202\373&9`\362[\332\322\336Sv\302\314\335\362\237\303*j\372\273\331\025s\245\vm\247\357\322\356\007\345Z\334\211\263\252\\352\250\242\370\331\226\246\177\275\2120\37 4\232\201\337\247\023k 4z]\234\274\225Q\2567;H \33603\333t\235"\337\373\200\026\262h\325\021$\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]\020@-.\rzY\022\001\300:\331\177\016\317Ao\346;\226j_\315\177[o?WU\355\320@F\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\362@\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\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 ".]???Z???I?????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

  • September 29, 2013 16:42

  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.

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• 

  katmai

  • September 29, 2013 17:10

  [quote="quizknows, post: 1471811">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.

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• 

  cPanelMichael

  • September 30, 2013 16:37

  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.

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• 

  quizknows

  • October 01, 2013 02:16

  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.

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