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Preventing-Brute-Force-SSH-AttacksMain.Preventing-Brute-Force-SSH-Attacks HistoryShow minor edits - Show changes to output Changed line 9 from:
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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. (:table border=1 bgcolor=#cccc99 cellspacing=0 :) (:cellnr:) [@ 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 (:table border=1 bgcolor=#cccc99 cellspacing=0 :) (:cellnr:) Port 23022 (:tableend:) In /etc/ssh/sshd_config, you can specify a list of allowed users like this: (:table border=1 bgcolor=#cccc99 cellspacing=0 :) (:cellnr:) AllowUsers itm admin [email protected] [email protected] (:tableend:) %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':'' (:table border=1 bgcolor=#cccc99 cellspacing=0 :) (:cellnr:) 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 (:tableend:) 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:) |