Difference between revisions of "Firewall Logs"

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| host||The Hostname of the system where this occurred (your server)
 
| host||The Hostname of the system where this occurred (your server)
 
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| kernel|Application (firewall rules are always kernel:)
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| kernel||Application (firewall rules are always kernel:)
 
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| DROP_ASL_INPUT||Firewall Rule Name
 
| DROP_ASL_INPUT||Firewall Rule Name

Revision as of 15:33, 24 March 2014

Contents

Log format

The ASL firewall will log a lot of information about a firewall event. A typical log entry may look like this:

Mar 24 14:11:11 host kernel: DROP_ASL_INPUT IN=eth0 OUT= MAC=00:50:56:bd:76:78:00:a0:c8:26:33:94:08:00 SRC=1.2.3.4 DST=5.6.7.8 LEN=48 TOS=0x00 PREC=0x00 TTL=115 ID=12197 CE DF MF PROTO=TCP SPT=3619 DPT=110 SEQ=1917628740 ACK=0 WINDOW=65535 RES=0x00 SYN URGP=0 OPT (020405B401010402)


Example Element Explanation
Mar 24 14:11:11 Date/Time Stamp
host The Hostname of the system where this occurred (your server)
kernel Application (firewall rules are always kernel:)
DROP_ASL_INPUT Firewall Rule Name
IN=eth0 Incoming Interface (This is only populated when the packet is coming into the server)
OUT= Outgoing Interface (This is only populated when the packet is going out of the server)
MAC=00:50:56:bd:76:78:00:a0:c8:26:33:94:08:00 The MAC Address of the last hop upstream hardware that send the packet (usually this will be your upstream router)
SRC=1.2.3.4 Source IP (The IP address for the system that sent this packet)
DST=5.6.7.8 Destination IP (The IP address the source system requested this packet be sent to)
LEN=48 Total length of IP packet in bytes
TOS=0x00 Type Of Service field. This is rarely used, and is replaced on most systems by DS and ECN.
PREC=0x00 The "Precedence" Type of Service field. This is rarely used, and is replaced on most systems by DS and ECN.
TTL=115 Remaining "Time To Live" for this packet in "hops"
ID=12197 Unique ID for this IP datagram. If this is a fragment, all fragments share the same ID.
CE ECN Flag, Congestion Experienced (optional)
DF Dont Fragment Flag (optional)
MF More Fragments to follow (optional)
PROTO=TCP Protocol (For example, TCP or UDP)
SPT=3619 Source Port (The port the packet came from)
DPT=110 Destination Port (The port the source IP requested the packet go to)
SEQ=1917628740 Receive Sequence number
ACK=0 Same as the Receive Sequence number above, but for the other end of the TCP connection. Normally only seen on the reply packet.
WINDOW=65535 The TCP Receive Window size.
RES=0x00 Reserved bits. This field is used, optionally, for things like ECNE and CWR.
SYN URGP=0 Packet Flags.
OPT (020405B401010402) TCP Options (optional)

Auditing rules

These rules do not block anything, they just log allowed traffic or special events.

Whitelists

ASL_WHITELIST

This logs when an IP on the firewall whitelist has been allowed to connect to the system. It does not block or shun anything.

Port Knocking

Advanced Port Knock System

ASL_KNOCK

This logs when a potential knock packet comes in when using the advanced portknocking system. It does not block or shun anything.

ASL_KNOCK_IN

This logs the IP of the source of a client when its connects to a portknock protected port. It does not block or shun anything.

Simple Port Knock System

ASL_SKNOCK

This logs when a potential knock packet comes in when using the simply portknocking system. It does not block or shun anything.

ASL_SKNOCK_IN

This logs the IP of the source of a client when its connects to a portknock protected port. It does not block or shun anything.

Blocking/Dropping rules

Automatic Blocks

ASL_AR_DROP

ASL has blocked packets from an IP that was automatically shunned by ASL.ASL_AUTOSHUN_BLOCK

User Defined Blocks

DROP_ASL_TORTIX

And IP address has been blocked from connecting the ASL web console based on the IP addresses you have configured to allow access. ASL does not block any IPs by default to the ASL web console.

ASL_SMTP_OUT

ASL has blocked a user that you have not authorized from sending SMTP traffic outbound. ASL does not block any users from sending SMTP traffic outbound by default.

ASL_BLACKLIST_BLOCK

ASL has blocked traffic from an IP that you placed on the ASL blacklist. This blacklist is manually created by the user, and ASL will not add IPs to this blacklist. The blacklist is empty by default.

ASL_GEO_BLOCK

ASL has blocked traffic from a country that you have configured ASL to block via ASLs geoblocking. This is manually configured by the user, and ASL will not automatically add countries to the geoblocking lists. No countries are blocked by default.

DROP_ASL_U_RATE

The Ratelimit you configured for this UDP port has been exceeded. ASL does not set any rate limits by default.


DROP_ASL_T_RATE

The Ratelimit you configured for this TCP port has been exceeded. ASL does not set any rate limits by default.

DROP_ASL_INPUT

ASL has dropped an inbound packet because you have configured it to do this. ASL does not block connections to any ports by default.

ASL_OUTPUT

ASL has dropped a packet because you have configured it to do this. ASL does not block outbound connections to any ports by default.

RBLS

ASL_TOR_BLOCK

ASL has blocked an IP that is a TOR exit node because you have configured ASL to block tor exit nodes. ASL does not block this by default.

ASL_AUTOSHUN_BLOCK

ASL has blocked an IP that is on the autoshun RBL list because you have configured ASL to block IPs from this RBL. ASL does not block this by default.

ASL_CIARMY_BLOCK

ASL has blocked an IP that is on the ciarmy RBL list because you have configured ASL to block IPs from this RBL. ASL does not block this by default.

ASL_DSHIELD_BLOCK

ASL has blocked an IP that is on the dshield RBL list because you have configured ASL to block IPs from this RBL. ASL does not block this by default.

ASL_ELASSO_BLOCK

ASL has blocked an IP that is on the spamhaus elasso RBL list because you have configured ASL to block IPs from this RBL. ASL does not block this by default.

ASL_LASSO_BLOCK

ASL has blocked an IP that is on the spamhaus lasso RBL list because you have configured ASL to block IPs from this RBL. ASL does not block this by default.

ASL_EMERGING_THREATS_BLOCK

ASL has blocked an IP that is on the emerging threats RBL list because you have configured ASL to block IPs from this RBL. ASL does not block this by default.

ASL_OPENBL_BLOCK

ASL has blocked an IP that is on the openbl RBL list because you have configured ASL to block IPs from this RBL. ASL does not block this by default.

ASL_OPENPROXIES_BLOCK

ASL has blocked an IP that is on the openproxies RBL list because you have configured ASL to block IPs from this RBL. ASL does not block this by default.

Bad Packets

ASL_FRAGMENT

ASL has blocked a fragmented packet. ASL, when configured properly, has a stateful firewall that will assemble fragmented packets. If this rule is triggered this means someone has either disabled stateful inspection for user defined rules, or the system is not using the ASL kernel and a third party kernel does not support stateful firewalls.

DROP_ASL_TOOSMALL

ASL has blocked a packet that is too small to be valid.

ASL_INVALID_INPUT

ASL had dropped an incoming invalid packet.

ASL_INVALID_FWD

ASL had dropped an invalid packet in the FORWARD chain.

ASL_INVALID_OUTPUT

ASL had dropped an outgoing invalid packet.

Port scans

DROP_ASL_ADVSCAN

ASL has detected and blocked a portscan using the advanced portscan detector in ASL.

DROP_ASL_PORTSCAN

ASL has detected and blocked a portscan.

DROP_ASL_GSCAN

ASL has detected a potential banner grab portscan.

DROP_ASL_CNSCAN

ASL has detected and blocked a connect() portscan.

DROP_ASL_SSCAN

ASL has detected and blocked a potential SYN portscan.

DROP_ASL_STSCAN

ASL has detected and blocked a stealth portscan.


DROP_ASL_MSS

ASL has detected a packet that is too small to be valid.

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