snort - capturar e dissecar o tráfego da rede

Snort - capturar e dissecar o trafego de rede

Ulisses Araujo Costa

[email protected]

25 Marco, 2009

Ulisses Araujo Costa Snort - capturar e dissecar o trafego de rede

Sumario

1 NIDS

2 Snort

3 Objectivo

4 tsharkEstatısticas


NIDS - Network Intrusion Detection System

Sistema de deteccao de intrusao de rede

Tenta detectar actividade maliciosa (ataques DoS, DDos, portscans, tentativas de cracking)


Como funciona

Analise de todos os pacotes

Tenta encontrar padroes suspeitos

Exemplo - port scanners

Se um grande numero de pedidos de coneccoes TCP para umgrande numero de portas diferentes num curto espaco de tempoentao o NIDS concluı que podemos estar a ser alvo de um scan deportos.


Sumario

1 NIDS

2 Snort

3 Objectivo



Definicao

SNORT r is an open source network intrusion preventionand detection system utilizing a rule-driven language,which combines the benefits of signature, protocol andanomaly based inspection methods. With millions ofdownloads to date, Snort is the most widely deployedintrusion detection and prevention technology worldwideand has become the de facto standard for the industry.

Modo passivo

Modo activo 6= firewall


Abordagem

Usar o Snort para capturar todo o trafego que conseguir em modopassivo.

root@pig:# snort -u snort -g snort -D -d -l /var/log/snort -c /etc/snort/snort.debian.conf -S -i

eth0

Grava log em binario (formato tcpdump)


Sumario

1 NIDS

2 Snort

3 Objectivo



Depois de ter o ficheiro. . .

Implementacao de filtros segundo determinadas regras

Agregacao de pacotes segundo regras (onde o Snort naochega)


Problema - parsing

Fazer parsing de tcpdump


Exemplo - pacote SSH


Implementacao em Haskell

getPacket :: [Word8] -> InPacket

getPacket bytes = toInPack $ listArray (0,Prelude.length bytes -1) $ bytes

-- Ethernet | IP | TCP | X

getPacketTCP :: [Word8] -> Maybe (NE.Packet (NI4.Packet (NT.Packet InPacket)))

getPacketTCP bytes = doParse $ getPacket bytes :: Maybe (NE.Packet (NI4.Packet (

NT.Packet InPacket)))

Problema

Nao ha parsers feitos para camada de aplicacao :S


Sumario

1 NIDS

2 Snort

3 Objectivo



Exemplos

Mostrar todas as comunicacoes com o IP 192.168.74.242root@pig:# tshark -R "ip.addr == 192.168.74.242" -r snort.log

...

7750 6079.816123 193.136.19.96 -> 192.168.74.242 SSHv2 Client: Key Exchange Init

7751 6079.816151 192.168.74.242 -> 193.136.19.96 TCP ssh > 51919 [ACK] Seq=37

Ack =825 Win =7424 Len=0 TSV =131877388 TSER =1789588

7752 6079.816528 192.168.74.242 -> 193.136.19.96 SSHv2 Server: Key Exchange Init

7753 6079.817450 193.136.19.96 -> 192.168.74.242 TCP 51919 > ssh [ACK] Seq =825


7754 6079.817649 193.136.19.96 -> 192.168.74.242 SSHv2 Client: Diffie -Hellman

GEX Request

7755 6079.820784 192.168.74.242 -> 193.136.19.96 SSHv2 Server: Diffie -Hellman

Key Exchange Reply

7756 6079.829495 193.136.19.96 -> 192.168.74.242 SSHv2 Client: Diffie -Hellman

GEX Init

7757 6079.857490 192.168.74.242 -> 193.136.19.96 SSHv2 Server: Diffie -Hellman

GEX Reply

7758 6079.884000 193.136.19.96 -> 192.168.74.242 SSHv2 Client: New Keys

7759 6079.922576 192.168.74.242 -> 193.136.19.96 TCP ssh > 51919 [ACK] Seq =1613


...


Exemplos

Mostrar um triplo com: (tempo,codigo http,tamanho do conteudohttp), separados por ’,’ e entre aspas.

root@pig:# tshark -r snort.log -R http.response -T fields -E header=y -E separator=’,’ -E

quote=d -e frame.time relative -e http.response.code -e http.content length

...

"128.341166000" ,"200" ,"165504"

"128.580181000" ,"200" ,"75332"

"128.711618000" ,"200" ,"1202"

"149.575548000" ,"206" ,"1"

"149.719938000" ,"304" ,

"149.882290000" ,"404" ,"338"

"150.026474000" ,"404" ,"341"

"150.026686000" ,"404" ,"342"

"150.170295000" ,"304" ,

"150.313576000" ,"304" ,

"150.456650000" ,"304" ,

...


Exemplos

Mostrar um tuplo de aridade 4 com: (tempo,ip origem,ip destino,tamanho do pacote tcp).

root@pig:# tshark -r snort.log -R "tcp.len>0" -T fields -e frame.time relative -e ip.src -e

ip.dst -e tcp.len

...

551.751252000 193.136.19.96 192.168.74.242 48

551.751377000 192.168.74.242 193.136.19.96 144

551.961545000 193.136.19.96 192.168.74.242 48

551.961715000 192.168.74.242 193.136.19.96 208

552.682260000 193.136.19.96 192.168.74.242 48

552.683955000 192.168.74.242 193.136.19.96 1448

552.683961000 192.168.74.242 193.136.19.96 1448

552.683967000 192.168.74.242 193.136.19.96 512

555.156301000 193.136.19.96 192.168.74.242 48

555.158474000 192.168.74.242 193.136.19.96 1448

555.158481000 192.168.74.242 193.136.19.96 1400

556.021205000 193.136.19.96 192.168.74.242 48

556.021405000 192.168.74.242 193.136.19.96 160

558.874202000 193.136.19.96 192.168.74.242 48

558.876027000 192.168.74.242 193.136.19.96 1448

...


Exemplos

Mostrar um triplo com: (ip origem,ip destino, porto do ip destino).

root@pig:# tshark -r snort.log -Tfields -e ip.src -e ip.dst -e tcp.dstport

...

192.168.74.242 193.136.19.96 37602

192.168.74.242 193.136.19.96 37602

193.136.19.96 192.168.74.242 22

192.168.74.242 193.136.19.96 37602

193.136.19.96 192.168.74.242 22

193.136.19.96 192.168.74.242 22

192.168.74.242 193.136.19.96 37602

192.168.74.242 193.136.19.96 37602

192.168.74.242 193.136.19.96 37602

193.136.19.96 192.168.74.242 22

193.136.19.96 192.168.74.242 22

193.136.19.96 192.168.74.242 22

193.136.19.96 192.168.74.242 22

192.168.74.242 193.136.19.96 37602

192.168.74.242 193.136.19.96 37602

...


Sumario

1 NIDS

2 Snort

3 Objectivo



Estatısticas

Hierarquia de protocolosroot@pig:# tshark -r snort.log -q -z io,phs

frame frames :7780 bytes :1111485

eth frames :7780 bytes :1111485

ip frames :3992 bytes :848025

tcp frames :3908 bytes :830990

ssh frames :2153 bytes :456686

http frames :55 bytes :19029





data -text -lines frames :10 bytes :5356

tcp.segments frames :3 bytes :1117


media frames :3 bytes :1117

udp frames :84 bytes :17035

nbdgm frames :50 bytes :12525

smb frames :50 bytes :12525

mailslot frames :50 bytes :12525

browser frames :50 bytes :12525

dns frames :34 bytes :4510

llc frames :3142 bytes :224934

stp frames :3040 bytes :182400

cdp frames :102 bytes :42534

loop frames :608 bytes :36480

data frames :608 bytes :36480

arp frames :38 bytes :2046


Estatısticas - Conversations

Usa-se: -z conv,<tipo>,<filtro>

Tipo pode ser: eth,tr,fc,fddi,ip,ipx,tcp,udpOs filtros servem para restringir as estatısticas

root@pig:# tshark -r snort.log -q -z conv,ip,tcp.port==80

================================================================================

IPv4 Conversations

Filter:tcp.port ==80

| <- | | -> | | Total |

|Frames Bytes | |Frames Bytes | |Frames Bytes |

193.136.19.148 <-> 192.168.74.242 141 13091 202 259651 343 272742

192.168.74.242 <-> 128.31.0.36 22 6858 28 4784 50 11642

================================================================================


Estatısticas - IO

Usa-se: -z io,stat,<int>,<filtro>,. . . ,<filtro>

root@pig:# tshark -r snort.log -q -z io,stat,300,’not (tcp.port=22)’

===================================================================

IO Statistics

Interval: 300.000 secs

Column #0:

| Column #0

Time |frames| bytes

000.000 -300.000 2161 543979

300.000 -600.000 1671 264877

600.000 -900.000 508 46224

900.000 -1200.000 185 12885

1200.000 -1500.000 201 14607

1500.000 -1800.000 187 13386

1800.000 -2100.000 189 13887

2100.000 -2400.000 187 13386

2400.000 -2700.000 189 13887

2700.000 -3000.000 187 13386

3000.000 -3300.000 185 12885

3300.000 -3600.000 189 13887

3600.000 -3900.000 210 15546

3900.000 -4200.000 189 13887

4200.000 -4500.000 187 13386

4500.000 -4800.000 185 12885

4800.000 -5100.000 189 13887

===================================================================


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snort - capturar e dissecar o tráfego da rede

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