Provided by: bld_0.3.4.1-4_amd64 
NAME
bld - A black list daemon
SYNOPSIS
bld -h | [option]
OPTIONS
-v Output version information and exit
-n Do not fork to become a daemon
-a address
Address to bind to
-p port
Port to listen to
-l number
Log verbosity (between 0 and 3)
-t number
Minimum time interval before blacklisting
-m number
Maximum submissions in time interval
-i number
IP list size
-b number
Blacklist size
-e number
Blacklist expiration
-P filename
Filename where to save PID
-T number
Timeout for client connections
-u user
User to run as
-g group
Group to run as
-f filename
Use a specific configuration file
-A filename
Filename where to find ACLs
-W filename
Filename where to find whitelist
-B filename
Filename where to store blacklist
-I filename
Filename where to store whole IP list
DESCRIPTION
By default, the bld daemon listens to requests on port 2905. Requests are either IP addresses
submissions or checks against the black list.
bld uses a very simple algorithm to decide whether to add IP addresses to the blacklist or not. The first
time an IP address is submitted, it is added to an internal list with a timestamp and all further
requests increment a counter for this IP. As soon as the minimum time interval is elapsed (default: 30
seconds), and if a maximum requests ratio is reached (default: 10 submissions in the 30 seconds
interval), the IP is put in the blacklist. It is then blacklisted for a configurable time (default: 900
seconds).
PROTOCOL
Requests sent to bld are rather simple. Each request or reply is followed by a linefeed and a carriage
return. A client may only send one request per TCP session. As of now, two commands may be used: ip
(address submission) and ip? (ask if address is blacklisted).
ip=a.b.c.d submits an IP address. The server acknowledges either with a 200 code if the address is not
blacklisted or a 421 if it is.
ipdecr=a.b.c.d decrements the internal counter for an IP address. The lowest value for the counter is
zero. The server always acknowledges with a 200 code.
ip?=a.b.c.d asks if address is blacklisted. The server reply may be 421 if it is or 200 if it's not.
ipbl=a.b.c.d forces the insertion in the blacklist. The server acknowledges with a 200 code.
If using IP based restrictions, the server reply may be 600 if the client is not in the correct ACL to
perform a request. Any other error will generate a reply with a 500 error code.
NOTES
bld binds to localhost by default and accepts any local request, so please make sure that only trusted
users can establish a connection to the daemon. Please check that all authorized hosts meet the minimal
security requirements before changing this parameter even if using an access control list (see
bld_acl.conf(5)).
bld will log some statistics if it receives the SIGUSR1 signal. SIGUSR2 is used to force a dump of both
lists in bld working directory.
FILES
/etc/bld/bld.conf /etc/bld/bld_acl.conf /etc/bld/bld_whitelist.conf /var/run/bld/bld.pid
/var/run/bld/bld_iplist.dump /var/run/bld/bld_blacklist.dump
SEE ALSO
bld.conf(5) bld_acl.conf(5) bld_whitelist.conf(5) bldread(8) bldquery(8) bldsubmit(8) blddecr(8)
AUTHOR
Olivier Beyssac <obld@r14.freenix.org> August 2004 BLD(8)