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Netcat ¼Ò°³¿Í Ȱ¿ë°¡À̵å
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Netcat ¼Ò°³¿Í Ȱ¿ë°¡À̵å

ÀÛ¼ºÀÚ : (ÁÖ)¼öÆÛÀ¯ÀúÄÚ¸®¾Æ, http://www.superuser.co.kr ¼­¹öÆÀ


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1. ¼Ò°³
2. ¼³Ä¡
3. ¿É¼Ç¼³¸í
4. »ç¿ë¹ý
5. Âü°í¹®Çå ¶Ç´Â URL



1. ¼Ò°³

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Netcat(ÀÌÇÏ nc·Î Ç¥±â)Àº Network connection ¿¡¼­ raw-data read, write¸¦ ÇÒ¼ö ÀÖ´Â À¯Æ¿¸®Æ¼ ÇÁ·Î±×·¥ÀÔ´Ï´Ù. ÀϹÝÀûÀ¸·Î´Â UNIXÀÇ cat°ú ºñ½ÁÇÑ »ç¿ë¹ýÀ» °¡Áö°í ÀÖÁö¸¸ catÀÌ ÆÄÀÏ¿¡ ¾²°Å³ª ÀеíÀÌ nc´Â ³×Æ®¿öÅ©¿¡ Àаųª ¾µ¼ö ÀÖ½À´Ï´Ù. À̰ÍÀº ½ºÅ©¸³Æ®¿Í º´¿ëÇÏ¿© network¿¡ ´ëÇÑ debugging, testing tool·Î½á ¸Å¿ì Æí¸®Çϰí, ¿øÇÏ´Â Æ÷Æ®·Î ¿øÇÏ´Â µ¥ÀÌÅ͸¦ ÁÖ°í¹ÞÀ»¼ö Àִ Ư¡¶§¹®¿¡ ÇØÅ·¿¡µµ ³Î¸® ÀÌ¿ëµÇ¸ç, ÄÄÇ»ÅÍ Æ÷·»½Ä¿¡ À־ ¶óÀ̺ê½Ã½ºÅÛÀÇ µ¥ÀÌÅ͸¦ ¼Õ»ó¾øÀÌ °¡Á®¿À±âÀ§Çؼ­µµ »ç¿ëµÉ¼ö ÀÖ½À´Ï´Ù.

ncÀº ¿øÇÏ´Â °ÅÀÇ ¸ðµç Á¾·ùÀÇ Á¢¼ÓÇüŸ¦ ¸¸µé¾î ³¾ ¼ö ÀÖ°í Èï¹Ì·Î¿î ¸î °¡Áö ³»Àå±â´ÉÀ» °®°í Àֱ⠶§¹®¿¡ ´Ù±â´ÉÀÇ ³×Å©¿öÅ© ¹®Á¦Çذá/Á¶»ç½Ã À¯¿ëÇÏ°Ô »ç¿ë°¡´ÉÇÕ´Ï´Ù.


2. ¼³Ä¡

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¸®´ª½º¿¡¼­ »ç¿ë°¡´ÉÇÑ ncÀº http://netcat.sourceforge.net/ ¿¡¼­ ´Ù¿î·Îµå ¹ÞÀ»¼ö ÀÖÀ¸¸ç RPM ,Source °¡ Á¦°øµË´Ï´Ù.

À©µµ¿ì¿¡¼­ ncÀ» »ç¿ëÇϽ÷Á¸é http://www.securityfocus.com/tools/139/scoreit ¿¡¼­ À©µµ¿ì¿ë nc¸¦ ´Ù¿î¹Þ¾Æ¼­ »ç¿ëÇϽǼö ÀÖ½À´Ï´Ù.

 


3. ¿É¼Ç¼³Á¤

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usage : nc [options] [target host] [ports]

-n : È£½ºÆ® ³×ÀÓ°ú Æ÷Æ®¸¦ ¼ýÀڷθ¸ ÀԷ¹޴´Ù.

-v : verbosity ¸¦ Áõ°¡ ½ÃŲ´Ù. ´õ ¸¹Àº Á¤º¸¸¦ ¾òÀ»¼ö ÀÖ´Ù.

-o [filename]: º¸³»°Å³ª ¹ÞÀº µ¥ÀÌÅ͸¦ Çí½º´ýÇÁÇÏ¿© ÆÄÀÏ¿¡ ÀúÀåÇÑ´Ù.

-u : TCP connection ´ë½Å¿¡ UDP connection ÀÌ ÀÌ·ç¾î Áø´Ù.

-p [port number or name] : local-port ¸¦ ÁöÁ¤ÇÑ´Ù. ÁÖ·Î -l °ú °°ÀÌ »ç¿ëÇÏ°Ô µÈ´Ù.

-s [ip address or DNS] : local ip address ¸¦ ÁöÁ¤ÇÑ´Ù. ¸ðµç Ç÷¿Æû¿¡¼­ Áö¿øµÇÁö´Â ¾Ê´Â´Ù.

-l : listen ¸ðµå·Î ncÀ» ¶ì¿ì°Ô µÈ´Ù. ´ç¿¬È÷ target host´Â ÀÔ·ÂÇÏÁö ¾Ê´Â´Ù. -p¿Í °°ÀÌ »ç¿ëÇÏ°Ô µÈ´Ù. nc¸¦ server ·Î¼­ ¾µ¶§ »ç¿ë.

-e [filename] : -DGAPING_SECURITY_HOLE ¿É¼ÇÀ¸·Î Make µÇ¾úÀ» ¶§ »ç¿ë°¡´ÉÇÏ´Ù.

connection ÀÌ ÀÌ·ç¾î Á³À» ¶§ fileÀ» exec ½ÃŲ´Ù. -l °ú °°ÀÌ »ç¿ëµÇ¸é ÇÑ instance¸¸À» »ç¿ëÇÏ´Â inetd¿Í ºñ½ÁÇÏ´Ù.

-t : -DTELNET ¿É¼ÇÀ¸·Î ÄÄÆÄÀÏ µÇ¾úÀ» ¶§ »ç¿ë°¡´ÉÇÏ´Ù. telnetd¿¡ Á¢¼ÓÀÌ °¡´ÉÇϵµ·Ï Á¢¼Ó½Ã telnet°ú °°Àº Çù»ó°úÁ¤À» °ÅÄ£´Ù.

-i [interval time] : nc´Â ÀϹÝÀûÀ¸·Î 8K ¾¿ µ¥ÀÌÅ͸¦ º¸³»°í ¹Þ´Âµ¥ ±×·¸°Ô Standard inputÀÇ ÇÑ ¶óÀξ¿ interval time¸¶´Ù º¸³»°Ô µÈ´Ù.

-z : connectionÀ» ÀÌ·ç±âÀ§ÇÑ ÃÖ¼ÒÇÑÀÇ µ¥ÀÌÅÍ ¿Ü¿¡´Â º¸³»Áö ¾Êµµ·Ï ÇÏ´Â ¿É¼Ç.

-r : port ÁöÁ¤ÀÌ ¿©·¯°³·Î µÇ¾î ÀÖÀ¸¸é À̶§ scanning ¼ø¼­¸¦ randomizeÇϰí (ÀϹÝÀûÀ¸·Î ¹üÀ§·Î ÁöÁ¤ÇÏ¸é ³ôÀº ¹øÈ£ÀÇ Æ÷Æ®ºÎÅÍ ½ºÄµÇÑ´Ù) ¶ÇÇÑ -p ¿É¼Ç¿¡¼­ ÁöÁ¤°¡´ÉÇÑ local portµµ randomize ÇÕ´Ï´Ù. À̶§ ÁÖÀÇ ÇÒ °ÍÀº -p°¡ -rÀ» override ÇÑ´Ù´Â °ÍÀÔ´Ï´Ù.

 


4. »ç¿ë¹ý

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multi-port connection

ncÀº ÇÑ È£½ºÆ®¿¡ ÇÑ ¹ø¿¡ ¿©·¯ connection À» ¸¸µé¼ö ÀÖ½À´Ï´Ù.
ÀÌ ¶§ ´ÙÀ½°ú °°ÀÌ ¿©·¯°³ÀÇ Æ÷Æ®¸¦ ±â¼úÇÒ ¼ö ÀÖ´Ù.

1. nc [target host] 20-30

ÀÌÈķΠǥÁØÀÔ·ÂÀ¸·Î ÀԷµǴ µ¥ÀÌÅ͵éÀº [target host] ÀÇ 20-30 »çÀÌ·Î ÇѲ¨¹ø¿¡ º¸³»Áö°Ô µË´Ï´Ù.


port scanning


[target host] ÀÇ ÁöÁ¤µÈ ¹üÀ§³»¿¡¼­ÀÇ ¾î¶² Æ÷Æ®°¡ ¾î¶»°Ô »ç¿ëµÇ°í ÀÖ´Â °¡¸¦ °Ë»öÇÒ ¼ö ÀÖ´Ù.

2. nc -v -w 3 -z 210.183.235.15 20-30, 70-90

À§ÀÇ ¸í·ÉÀº ´ÙÀ½ °á°ú¿Í °°ÀÌ 20-30, 70-90 ±îÁöÀÇ Æ÷Æ®µé¿¡ ´ëÇÑ Á¤º¸¸¦ º¸¿©ÁØ´Ù.

3. [root@tsc13 ~/work]

4. # nc -v -w 3 -z ostsc.co.kr 20-30, 70-90

5. DNS fwd/rev mismatch: ostsc.co.kr.ostsc.co.kr != ns.ostsc.co.kr

6. ostsc.co.kr.ostsc.co.kr [210.183.235.13] 22 (ssh) open

7. ostsc.co.kr.ostsc.co.kr [210.183.235.13] 80 (http) open

8. ostsc.co.kr.ostsc.co.kr [210.183.235.13] 79 (finger) open

À̰ͺ¸´Ù ´õ ÀÚ¼¼ÇÑ Á¤º¸¸¦ ¾ò°íÀÚ ÇÒ¶§´Â

9. echo QUIT l nc -v -w 3 [target host] [ports] ¶ó°í Çϸé ÀÀ´äÀ̳ª ¿¡·¯¸Þ¼¼Áö·Î ºÎÅÍ ¹öÀü Á¤º¸ µîµµ ¾òÀ» ¼ö ÀÖ½À´Ï´Ù.

¾Æ·¡ÀÇ ½ÇÇà°á°ú¸¦ º¸¸é °¢ Æ÷Æ®¿¡¼­ ¾Ë·ÁÁÖ´Â ¸Þ¼¼Áö¸¦ È®ÀÎ ÇÒ ¼ö ÀÖ½À´Ï´Ù.

10. [root@tsc13 ~/work]

11. # echo QUIT|nc -v -w 3 ostsc.co.kr 10-80

12. DNS fwd/rev mismatch: ostsc.co.kr.ostsc.co.kr != ns.ostsc.co.kr

13. ostsc.co.kr.ostsc.co.kr [210.183.235.13] 80 (http) open

14. <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">

15. <html><head>

16. <title>501 Method Not Implemented</title>

17. </head><body>

18. <h1>Method Not Implemented</h1>

19. <p>QUIT to /index.html not supported.<br />

20. </p>

21. <hr />

22. <address>Apache/2.0.51 (Fedora) Server at 210.183.235.13 Port 80</address>

23. </body></html>

24. ostsc.co.kr.ostsc.co.kr [210.183.235.13] 79 (finger) open

25. ** UNAUTHORIZED ACCESS PROHIBITED *** YOUR CONNECTION ATTEMPT HAS BEEN LOGGED. GO AWAY.ostsc.co.kr.ostsc.co.kr [210.183.235.13] 53 (domain) open

26. ostsc.co.kr.ostsc.co.kr [210.183.235.13] 22 (ssh) open

27. ostsc.co.kr.ostsc.co.kr [210.183.235.13] 15 (netstat) open

28. ** UNAUTHORIZED ACCESS PROHIBITED *** YOUR CONNECTION ATTEMPT HAS BEEN LOGGED. GO AWAY.ostsc.co.kr.ostsc.co.kr [210.183.235.13] 11 (systat) open

29. ** UNAUTHORIZED ACCESS PROHIBITED *** YOUR CONNECTION ATTEMPT HAS BEEN LOGGED. GO AWAY.

ncÀ» ÀÌ¿ëÇÏ¿© DATA¸¦ Àü¼ÛÇÏ´Â ¹æ¹ýÀ» ¾Ë¾Æº¸°Ú½À´Ï´Ù.

Àü¼Û¹ÞÀ» ½Ã½ºÅÛ¿¡¼­´Â ncÀ» ´ë±â¸ðµå·Î ÀÛµ¿½ÃÄÑ µÓ´Ï´Ù.

30. nc -l -p 1234 l uncompress -c l tar xvfp -

µ¥ÀÌÅ͸¦ º¸³¾ ½Ã½ºÅÛ¿¡¼­´Â ¾Æ·¡Ã³·³ ¸í·ÉÀ» ³»¸³´Ï´Ù

31. tar cfp - /some/dir l compress -c l nc -w 3 [other machine] 1234

¼º´ÉÅ×½ºÆ®

nc¸¦ ÀÌ¿ëÇØ¼­ Å« µ¥ÀÌÅ͸¦ ¼­·Î º¸³»°í ¹ÞÀ½À¸·Î½á networkÀÇ performance¸¦ Å×½ºÆ®ÇÒ¼ö ÀÖ½À´Ï´Ù.
¼­·Î ¼ø¼­¸¦ ´Þ¸®Çؼ­ ÇØ º¸¾Ò½À´Ï´Ù.

A ¼­¹ö

32. $ yes BBBBBBBBBBBBBBBBBBBBBB l /tmp/nc x.x.x.x 2222 >/dev/null
Broken pipe
$ yes AAAAAAAAAAAAAAAAAAAAAA l /tmp/nc -v -v -l -p 2222 >/dev/null
listening on [any] 2222 ...
connect to [x.x.x.x] from x.x.x.x [x.x.x.x] 2790
sent 6643712, rcvd 9542784

A°¡ ¸¹ÀÌ ¹ÞÀ½ B ¼­¹ö

33. $ yes AAAAAAAAAAAAAAAAAAAAAA l nc -v -v -l -p 2222 >/dev/null
listening on [any] 2222 ...
203.239.110.12: inverse host lookup failed: Unknown host
connect to [x.x.x.x] from (UNKNOWN) [x.x.x.x] 1672
sent 11145216, rcvd 8092008
$ yes BBBBBBBBBBBBBBBBBBBBBB l nc x.x.x.x 2222 >/dev/null
Broken pipe

B°¡ ¸¹ÀÌ º¸³¿

ÇÁ·Î±×·¥¿¡¼­ Ȱ¿ë

½© ½ºÅ©¸³Æ®¿¡¼­ µ¥ÀÌÅÍÀÇ Àü¼Û¿¡ »ç¿ëÇÒ¼öµµ º¸³¾ ¼ö ÀÖ½À´Ï´Ù


ÄÄÇ»ÅÍ Æ÷·»½Ä¿¡ Ȱ¿ë

ºÐ¼®ÇÒ ½Ã½ºÅÛ¿¡¼­ ncÀ» ÀÌ¿ëÇØ¼­ Á¶»ç´ë»ó ½Ã½ºÅÛÀ¸·ÎºÎÅÍ º¹»çÇÒ ÆÄƼ¼ÇÀ» ÀúÀåÇϵµ·Ï ¼³Á¤ÇØ µÓ´Ï´Ù.

34. #nc -l -p 10000 > target.hda2.dd

Á¶»ç´ë»ó ½Ã½ºÅÛ¿¡¼­ dd ¸í·ÉÀ» ÀÌ¿ëÇØ¼­ ÆÄƼ¼ÇÀ» º¹»çÇϰí À̸¦ ncÀ» ÀÌ¿ëÇØ¼­ ºÐ¼®ÇÒ ½Ã½ºÅÛÀ¸·Î Àü¼ÛÇÕ´Ï´Ù.

35. #dd if=/dev/hda2 bs=1024 | nc 210.183.234.15 10000 -w 3


5. Âü°í¹®Çå ¶Ç´Â URL

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http://security.kaist.ac.kr/docs/netcat.html

http://www.oac.uci.edu/indiv/franklin/doc/netcat.html


 

[¿ø±Û¸µÅ©] : https://www.linux.co.kr/home2/board/subbs/board.php?bo_table=lecture&wr_id=1204


ÀÌ ±ÛÀ» Æ®À§ÅÍ·Î º¸³»±â ÀÌ ±ÛÀ» ÆäÀ̽ººÏÀ¸·Î º¸³»±â ÀÌ ±ÛÀ» ¹ÌÅõµ¥ÀÌ·Î º¸³»±â

 
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¸®´ª½º¸¶½ºÅÍ 1±Þ,2±Þ Àü¹®À§¿ø(ÃâÁ¦)(Çѱ¹Á¤º¸Åë½ÅÁøÈïÇùȸ, 2005³â~)
SULinux 1.0, 1.5, 2.0, 2014 °³¹ß ÃѰý(sulinux.net, 1998³â~)
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