openvassd - The Scanner of the Open Vulnerability Assessment System (OpenVAS)
openvassd [-v] [-h] [-c config-file] [-D] [-R] [-P]
is a security auditing framework made up of several modules. The
is in charge of executing many security tests
against many target hosts in a highly optimized way.
inspects the remote hosts and attempts to list all the
vulnerabilities and common misconfigurations that affects them. Note that
openvassd will run in daemon mode by default (unless you specify -f as an
- -c <config-file>,
- Use the alternate configuration file instead of
- -f, --foreground
- Make the scanner stay in foreground (non-daemon mode)
- -v, --version
- Writes the version number and exits
- -h, --help
- Show a summary of the commands
The default openvassd
contains these options:
- Contains the location of the plugins folder. This is usually
/var/lib/openvas/plugins, but you may change this.
- path to the logfile. You can enter syslog if you want the openvassd
messages to be logged via syslogd You may also enter stderr
if you want the openvassd logs to be written on stderr. Because
openvassd is a sensitive program, you should keep your logs.
- is maximum number of hosts to test at the same time which should be given
to the client (which can override it). This value must be computed given
your bandwidth, the number of hosts you want to test, your amount of
memory and the horsepower of your processor(s).
- is the number of plugins that will run against each host being tested.
Note that the total number of process will be max_checks x
max_hosts so you need to find a balance between these two options.
Note that launching too many plugins at the same time may disable the
remote host, either temporarily (ie: inetd closes its ports) or definitely
(the remote host crash because it is asked to do too many things at the
same time), so be careful.
- If this option is set to 'yes', then each child forked by openvassd will
nice(2) itself to a very low priority. This may speed up your scan as the
main openvassd process will be able to continue to spew processes, and
this guarantees that openvassd does not deprives other important processes
from their resources.
- If this option is set to 'yes', openvassd will store the name, pid, date
and target of each plugin launched. This is helpful for monitoring and
debugging purpose, however this option might make openvassd fill your disk
- If this option is set to 'yes', openvassd will log the name of each plugin
being loaded at startup, or each time it receives the HUP signal.
- Some plugins might issue messages, most of the time to inform you that
something went wrong. If you want to read these messages, set this value
to a given file name. If you want to save space, set this option value to
- By default, openvassd looks for default CGIs in /cgi-bin and /scripts. You
may change these to something else to reflect the policy of your site. The
syntax of this option is the same as the shell $PATH variable:
- This is the default range of ports that the scanner plugins will probe.
The syntax of this option is flexible, it can be a single range
("1-1500"), several ports ("21,23,80"), several ranges
of ports ("1-1500,32000-33000"). Note that you can specify UDP
and TCP ports by prefixing each range by T or U. For instance, the
following range will make openvassd scan UDP ports 1 to 1024 and TCP ports
1 to 65535 : "T:1-65535,U:1-1024".
- By default, openvassd does not trust the remote host banners. It means
that it will check a webserver claiming to be IIS for Apache flaws, and so
on. This behavior might generate false positive and will slow the scan
down somehow. If you are sure the banners of the remote host have not been
tampered with, you can safely enable this option, which will force the
plugins to perform their job only against the services they have been
designed to check.
- Number of seconds that the security checks will wait for when doing a
recv(). You should increase this value if you are running openvassd across
a slow network slink (testing a host via a dialup connection for instance)
- Number of retries when a socket connection attempt timesout.
- Some services (in particular SMB) do not appreciate multiple connections
at the same time coming from the same host. This option allows you to
prevent openvassd to make two connections on the same given ports at the
same time. The syntax of this option is "port1[, port2....]".
Note that you can use the KB notation of openvassd to designate a service
formally. Ex: "139, Services/www", will prevent openvassd from
making two connections at the same time on port 139 and on every port
which hosts a web server.
- This is the maximum lifetime, in seconds of a plugin. It may happen that
some plugins are slow because of the way they are written or the way the
remote server behaves. This option allows you to make sure your scan is
never caught in an endless loop because of a non-finishing plugin. Doesn't
affect ACT_SCANNER plugins.
- Like plugins_timeout, but for ACT_SCANNER plugins.
- Most of the time, openvassd attempts to reproduce an exceptional condition
to determine if the remote services are vulnerable to certain flaws. This
includes the reproduction of buffer overflows or format strings, which may
make the remote server crash. If you set this option to 'yes', openvassd
will disable the plugins which have the potential to crash the remote
services, and will at the same time make several checks rely on the banner
of the service tested instead of its behavior towards a certain input.
This reduces false positives and makes openvassd nicer towards your
network, however this may make you miss important vulnerabilities (as a
vulnerability affecting a given service may also affect another one).
- OpenVAS plugins use the result of each other to execute their job. For
instance, a plugin which logs into the remote SMB registry will need the
results of the plugin which finds the SMB name of the remote host and the
results of the plugin which attempts to log into the remote host. If you
want to only select a subset of the plugins available, tracking the
dependencies can quickly become tiresome. If you set this option to 'yes',
openvassd will automatically enable the plugins that are depended on.
- Set this option to 'yes' if you are testing your local network and each
local host has a dynamic IP address (affected by DHCP or BOOTP), and all
the tested hosts will be referred to by their MAC address.
- Name of the network interface that will be used as the source of
connections established by OpenVAS. The scan won't be launched if the
value isn't authorized according to (sys_)ifaces_allow / (sys_)ifaces_deny
- Comma-separated list of interfaces names that are authorized as
- Comma-separated list of interfaces names that are not authorized as
- Like ifaces_allow. Can't be overridden by the client.
- Like ifaces_deny. Can't be overridden by the client.
- Comma-separated list of the only targets that are authorized to be
scanned. Supports the same syntax as the list targets. Both target
hostnames and the address to which they resolve are checked. Hostnames in
hosts_allow list are not resolved however.
- Comma-separated list of targets that are not authorized to be scanned.
Supports the same syntax as the list targets. Both target hostnames and
the address to which they resolve are checked. Hostnames in hosts_deny
list are not resolved however.
- Like hosts_allow. Can't be overridden by the client.
- Like hosts_deny. Can't be overridden by the client.
The other options in this file can usually be redefined by the client.
At log in attempt, openvassd checks that the certificate has been signed by
a recognized authority.
Bear in mind that OpenVAS can be quite network intensive. Even if the OpenVAS
developers have taken every effort to avoid packet loss (including
transparently resending UDP packets, waiting for data to be received in TCP
connections, etc.) so bandwidth use should always be closely monitored, with
current server hardware, bandwidth is usually the bottleneck in a OpenVAS
scan. It might not became too apparent in the final reports, scanners will
still run, holes might be detected, but you will risk to run into false
(i.e. OpenVAS will not report a security hole that is present in
a remote host)
Users might need to tune OpenVAS configuration if running the scanner in low
bandwidth conditions ( low
being 'less bandwidth that the one your
hardware system can produce) or otherwise will get erratic results. There are
several parameters that can be modified to reduce network load:
- (Introduced in OpenVAS 0.99.4) The default value is set to 5 seconds, that
can (should) be increased if network bandwidth is low in the
openvassd.conf or openvasrc configuration files. Notice that it is
recommended to increase this this value, if you are running a test outside
your LAN (i.e. to Internet hosts through an Internet connection), to over
- Number of hosts to test at the same time (this value is set by the OpenVAS
GUI client or by .openvasrc) it can be as low as you want it to be
(obviously 1 is the minimum)
- Number of checks to test at the same time (this value is also set by the
OpenVAS GUI client or by .openvasrc ) it can be as low as you want it to
be and it will also reduce network load and improve performance (obviously
1 is the minimum) Notice that the OpenVAS scanner will spawn max_hosts *
Other options might be using the QoS features offered by your server
operating system or your network to improve the bandwidth use.
It is not easy to give a bandwidth estimate for a OpenVAS run, you will
probably need to make your own counts. However, assuming you test 65536
TCP ports. This will require at least a single packet per port that is at
least 40 bytes large. Add 14 bytes for the ethernet header and you will
send 65536 * (40 + 14) = 3670016 bytes. So for just probing all TCP ports
we may need a multitude of this as nmap will try to resend the packets
twice if no response is received.
A very rough estimate is that a full scan for UDP, TCP and RPC as well as
all NASL scripts may result in 8 to 32 MB worth of traffic per scanned
host. Reducing the amount of tested part and such will reduce the amount
of data to be transferred significantly.
The canonical places where you will find more information about the OpenVAS
http://www.openvas.org/ (Official site)
http://wald.intevation.org/projects/openvas/ (Developers site)
http://bugs.openvas.org (Bug Tracker)
openvassd was forked from nessusd in 2005. Nessusd was written by Renaud
Deraison <firstname.lastname@example.org>. Since 2005 the OpenVAS development
team improved and extended the tool.