Of these firewall rules, which among the following would be appropriate?

Study the log given below and answer the following question:

Apr 24 14:46:46 [4663]: spp_portscan: portscan detected from 194.222.156.169 Apr 24 14:46:46 [4663]: IDS27/FIN Scan: 194.222.156.169:56693 -> 172.16.1.107:482 Apr 24 18:01:05 [4663]: IDS/DNS-version-query: 212.244.97.121:3485 -> 172.16.1.107:53 Apr 24 19:04:01 [4663]: IDS213/ftp-passwd-retrieval: 194.222.156.169:1425 -> 172.16.1.107:21 Apr 25 08:02:41 [5875]: spp_portscan: PORTSCAN DETECTED from 24.9.255.53 Apr 25 02:08:07 [5875]: IDS277/DNS-version-query: 63.226.81.13:4499 -> 172.16.1.107:53 Apr 25 02:08:07 [5875]: IDS277/DNS-version-query: 63.226.81.13:4630 -> 172.16.1.101:53

Apr 25 02:38:17 [5875]: IDS/RPC-rpcinfo-query: 212.251.1.94:642 -> 172.16.1.107:111 Apr 25 19:37:32 [5875]: IDS230/web-cgi-space-wildcard: 198.173.35.164:4221 -> 172.16.1.107:80 Apr 26 05:45:12 [6283]: IDS212/dns-zone-transfer: 38.31.107.87:2291 -> 172.16.1.101:53 Apr 26 06:43:05 [6283]: IDS181/nops-x86: 63.226.81.13:1351 -> 172.16.1.107:53 Apr 26 06:44:25 victim7 PAM_pwdb[12509]: (login) session opened for user simple by (uid=0) Apr 26 06:44:36 victim7 PAM_pwdb[12521]: (su) session opened for user simon by simple(uid=506)
Apr 26 06:45:34 [6283]: IDS175/socks-probe: 24.112.167.35:20 -> 172.16.1.107:1080 Apr 26 06:52:10 [6283]: IDS127/telnet-login-incorrect: 172.16.1.107:23 -> 213.28.22.189:4558

Precautionary measures to prevent this attack would include writing firewall rules. Of these firewall rules, which among the following would be appropriate?

Study the log given below and answer the following question:

Apr 24 14:46:46 [4663]: spp_portscan: portscan detected from 194.222.156.169 Apr 24 14:46:46 [4663]: IDS27/FIN Scan: 194.222.156.169:56693 -> 172.16.1.107:482 Apr 24 18:01:05 [4663]: IDS/DNS-version-query: 212.244.97.121:3485 -> 172.16.1.107:53 Apr 24 19:04:01 [4663]: IDS213/ftp-passwd-retrieval: 194.222.156.169:1425 -> 172.16.1.107:21 Apr 25 08:02:41 [5875]: spp_portscan: PORTSCAN DETECTED from 24.9.255.53 Apr 25 02:08:07 [5875]: IDS277/DNS-version-query: 63.226.81.13:4499 -> 172.16.1.107:53 Apr 25 02:08:07 [5875]: IDS277/DNS-version-query: 63.226.81.13:4630 -> 172.16.1.101:53

Apr 25 02:38:17 [5875]: IDS/RPC-rpcinfo-query: 212.251.1.94:642 -> 172.16.1.107:111 Apr 25 19:37:32 [5875]: IDS230/web-cgi-space-wildcard: 198.173.35.164:4221 -> 172.16.1.107:80 Apr 26 05:45:12 [6283]: IDS212/dns-zone-transfer: 38.31.107.87:2291 -> 172.16.1.101:53 Apr 26 06:43:05 [6283]: IDS181/nops-x86: 63.226.81.13:1351 -> 172.16.1.107:53 Apr 26 06:44:25 victim7 PAM_pwdb[12509]: (login) session opened for user simple by (uid=0) Apr 26 06:44:36 victim7 PAM_pwdb[12521]: (su) session opened for user simon by simple(uid=506)
Apr 26 06:45:34 [6283]: IDS175/socks-probe: 24.112.167.35:20 -> 172.16.1.107:1080 Apr 26 06:52:10 [6283]: IDS127/telnet-login-incorrect: 172.16.1.107:23 -> 213.28.22.189:4558

Precautionary measures to prevent this attack would include writing firewall rules. Of these firewall rules, which among the following would be appropriate?

A.
Disallow UDP53 in from outside to DNS server

B.

Allow UDP53 in from DNS server to outside

C.
Disallow TCP53 in from secondaries or ISP server to DNS server

D.
Block all UDP traffic

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val

val

more of the question, how, disabling UDP 53 going to stop an attacker? if TCP still enabled any type of scan still avaiable for an attacker.

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Ay

Ay

From the log, one of the things the attacker was trying to do is initiate an unauthorized dns client query. Blocking UDP 53 would prevent it, that way, the fw only permit traffic that is in response to a query from within. tcp 53 is used in zone transfer.

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