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Preventing-Brute-Force-SSH-Attacks

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''Use tools like DenyHosts or Fail2ban''

''Use
'hashlimit' in 'iptables':''
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!!Use tools like DenyHosts or Fail2ban

!!Use
'hashlimit' in 'iptables:
October 31, 2011, at 06:58 AM by 117.99.109.84 -
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(:Google1:)
(:Googlemm:)
----
!!Preventing Brute Force SSH Attacks
----



If you will always be connecting to your server from the same IP address, you can firewall off port 22 to everything EXCEPT your own IP address.

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[@
iptables -A INPUT -p tcp -d 0/0 -s your-ip-address --dport 22 -j ACCEPT
iptables -A INPUT -p tcp -d 0/0 --dport 22 -j DROP
]@
(:tableend:)

%red%Then run 'iptables-save'%%


''Hide from automated attackers. ''

To configure this, just change the Port line in /etc/ssh/sshd_config and restart ssh

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Port 23022
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In /etc/ssh/sshd_config, you can specify a list of allowed users like this:

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AllowUsers itm admin root@192.168.1.2 root@192.168.1.1
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%blue%This will allow users 'itm' and 'admin' to log in from anywhere, and root is only allowed to log in from those two IP addresses.%%


''Use tools like DenyHosts or Fail2ban''

''Use 'hashlimit' in 'iptables':''

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iptables -I INPUT -m hashlimit -m tcp -p tcp --dport 23032 --hashlimit 1/min
--hashlimit-mode srcip --hashlimit-name ssh -m state --state NEW -j ACCEPT
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This rule limits one connection to the SSH port from one IP address per minute.

[@
root@server3:~# iptables -m hashlimit -help
iptables v1.4.10

Usage: iptables -[AD] chain rule-specification [options]
iptables -I chain [rulenum] rule-specification [options]
iptables -R chain rulenum rule-specification [options]
iptables -D chain rulenum [options]
iptables -[LS] [chain [rulenum]] [options]
iptables -[FZ] [chain] [options]
iptables -[NX] chain
iptables -E old-chain-name new-chain-name
iptables -P chain target [options]
iptables -h (print this help information)

''Commands'':
Either long or short options are allowed.
--append -A chain Append to chain
--delete -D chain Delete matching rule from chain
--delete -D chain rulenum
Delete rule rulenum (1 = first) from chain
--insert -I chain [rulenum]
Insert in chain as rulenum (default 1=first)
--replace -R chain rulenum
Replace rule rulenum (1 = first) in chain
--list -L [chain [rulenum]]
List the rules in a chain or all chains
--list-rules -S [chain [rulenum]]
Print the rules in a chain or all chains
--flush -F [chain] Delete all rules in chain or all chains
--zero -Z [chain [rulenum]]
Zero counters in chain or all chains
--new -N chain Create a new user-defined chain
--delete-chain
-X [chain] Delete a user-defined chain
--policy -P chain target
Change policy on chain to target
--rename-chain
-E old-chain new-chain
Change chain name, (moving any references)
Options:
[!] --proto -p proto protocol: by number or name, eg. `tcp'
[!] --source -s address[/mask][...]
source specification
[!] --destination -d address[/mask][...]
destination specification
[!] --in-interface -i input name[+]
network interface name ([+] for wildcard)
--jump -j target
target for rule (may load target extension)
--goto -g chain
jump to chain with no return
--match -m match
extended match (may load extension)
--numeric -n numeric output of addresses and ports
[!] --out-interface -o output name[+]
network interface name ([+] for wildcard)
--table -t table table to manipulate (default: `filter')
--verbose -v verbose mode
--line-numbers print line numbers when listing
--exact -x expand numbers (display exact values)
[!] --fragment -f match second or further fragments only
--modprobe=<command> try to insert modules using this command
--set-counters PKTS BYTES set the counter during insert/append
[!] --version -V print package version.


''hashlimit match options'':
--hashlimit-upto <avg> max average match rate
[Packets per second unless followed by
/sec /minute /hour /day postfixes]
--hashlimit-above <avg> min average match rate
--hashlimit-mode <mode> mode is a comma-separated list of
dstip,srcip,dstport,srcport (or none)
--hashlimit-srcmask <length> source address grouping prefix length
--hashlimit-dstmask <length> destination address grouping prefix length
--hashlimit-name <name> name for /proc/net/ipt_hashlimit
--hashlimit-burst <num> number to match in a burst, default 5
--hashlimit-htable-size <num> number of hashtable buckets
--hashlimit-htable-max <num> number of hashtable entries
--hashlimit-htable-gcinterval interval between garbage collection runs
--hashlimit-htable-expire after which time are idle entries expired?

root@server3:~#
@]
(:Google1:)
(:Googlemm:)
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Page last modified on November 01, 2011, at 07:02 AM