Provided by: openvas-scanner_22.7.9-1ubuntu3_amd64 
NAME
openvas - The Scanner of the Greenbone Vulnerability Management
SYNOPSIS
openvas [-V] [-h] [-c config-file] [--scan-start scan-uuid] [-u] [-s] [-y]
DESCRIPTION
Greenbone Vulnerability Management (GVM) is a vulnerability auditing and management framework made up of
several modules. The OpenVAS Scanner, openvas is in charge of executing many security tests against many
target hosts in a highly optimized way.
openvas inspects the remote hosts to list all the vulnerabilities and common misconfigurations that
affects them.
It is a command line tool with parameters to update the feed of vulnerability tests and to start a scan.
The second part of the interface is the redis store where the parameters about a scan task need to be
placed and from where the results can be retrieved.
OPTIONS
-c <config-file>, --config-file=<config-file>
Use the alternate configuration file instead of /etc/openvas/openvas.conf
-V, --version
Prints the version number and exits
-h, --help
Show a summary of the commands
--scan-start=<scan-uuid>
ID for a single scan task. The scanner will start the scan with the data already loaded in a redis
KB, which will be found using the given scan-id.
--scan-stop=<scan-uuid>
ID for a single scan task. The scanner will search the redis kb associated to the given scan_id.
It takes the pid from the kb and sends the SIGUSR1 kill signal to stop the scan.
-u, --update-vt-info
Updates VT info into redis store from VT files.
THE CONFIGURATION FILE
The default openvas configuration file, /etc/openvas/openvas.conf contains these options:
plugins_folder
Contains the location of the plugins folder. This is usually /var/lib/openvas/plugins, but you may
change this.
max_hosts
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).
max_checks
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.
log_whole_attack
If this option is set to 'yes', openvas 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
openvas fill your disk rather quickly.
debug_tls
This is an scanner-only option which allows you to set the TLS log level. The level is an integer
between 0 and 9. Higher values mean more verbosity and might make openvas fill your disk rather
quickly. The default value is 0 (disabled).
Larger values should only be used with care, since they may reveal sensitive information in the
scanner logs.
Use a debug level over 10 to enable all debugging options.
log_plugins_name_at_load
If this option is set to 'yes', openvas will log the name of each plugin being loaded at startup,
or each time it receives the HUP signal.
cgi_path
By default, openvas 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: path1:path2:...
port_range
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 openvas scan UDP ports 1 to 1024 and TCP
ports 1 to 65535 : "T:1-65535,U:1-1024".
test_alive_hosts_only
If this option is set to 'yes', openvas will scan the target list for alive hosts in a separate
process while only testing those hosts which are identified as alive. This boosts the scan speed
of target ranges with a high amount of dead hosts significantly.
optimize_test
By default, optimize_test is enabled which means openvas does trust the remote host banners and is
only launching plugins against the services they have been designed to check. For example it will
check a web server claiming to be IIS only for IIS related flaws but will skip plugins testing for
Apache flaws, and so on. This default behavior is used to optimize the scanning performance and to
avoid false positives. If you are not sure that the banners of the remote host have been tampered
with, you can disable this option.
test_empty_vhost
If set to yes, the scanner will also test the target by using empty vhost value in addition to the
target's associated vhost values.
checks_read_timeout
Number of seconds that the security checks will wait for when doing a recv(). You should increase
this value if you are running openvas across a slow network slink (testing a host via a dialup
connection for instance)
timeout_retry
Number of retries when a socket connection attempt timesout.
open_sock_max_attempts
When a port is found as opened at the beginning of the scan, and for some reason the status
changes to filtered/closed, it will not be possible to open a socket. This is the number of
unsuccessful retries to open the socket before to set the port as closed. This avoids to launch
plugins which need the opened port as a mandatory key, therefore it avoids an overlong scan
duration. If the set value is 0 or a negative value, this option is disabled. It should be take in
account that one unsuccessful attempt needs the number of retries set in "timeout_retry".
time_between_request
Some devices do not appreciate quick connection establishment and termination neither quick
request. This option allows you to set a wait time between two actions like to open a tcp socket,
to send a request through the open tcp socket, and to close the tcp socket. This value should be
given in milliseconds. If the set value is 0 (default value), this option is disabled and there is
no wait time between requests.
expand_vhosts
Whether to expand the target host's list of vhosts with values gathered from sources such as
reverse-lookup queries and VT checks for SSL/TLS certificates.
non_simult_ports
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 openvas 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 openvas to designate a service formally. Ex: "139, Services/www", will
prevent openvas from making two connections at the same time on port 139 and on every port which
hosts a web server.
allow_simultaneous_ips
If set to no, this option prevent openvas to scan more than one different IPs (e.g. the IPv4 and
IPv6 addresses) which belong to the same host at the same time. Default, yes.
plugins_timeout
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.
scanner_plugins_timeout
Like plugins_timeout, but for ACT_SCANNER plugins.
max_vts_timeouts
During a scan it might happen that a host unexpectedly shuts down, a firewall blocks the traffic,
a network device issue break the connection, etc. This leads to many NVT timeouts and long scan
durations. This option checks the alive status of the host again after the provided amount of max
NVT timeouts are reached. If the host is considered dead the scan will be stopped for this host.
Otherwise the scan will continue. This option requires Boreas alive test to be enabled. Default:
option not set, disabled.
safe_checks
Most of the time, openvas 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', openvas 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 openvas nicer towards
your network, however this may make you miss important vulnerabilities (as a vulnerability
affecting a given service may also affect another one).
auto_enable_dependencies
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', openvas will automatically enable the plugins
that are depended on.
hosts_allow
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.
hosts_deny
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.
sys_hosts_allow
Like hosts_allow. Can't be overridden by the client.
sys_hosts_deny
Like hosts_deny. Can't be overridden by the client.
max_sysload
Maximum load on the system. Once this load is reached, no further VTs are started until the load
drops below this value again.
min_free_mem
Minimum available memory (in MB) which should be kept free on the system. Once this limit is
reached, no further VTs are started until sufficient memory is available again.
The other options in this file can usually be redefined by the client.
NETWORK USAGE
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 negatives (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:
checks_read_timeout
The default value is set to 5 seconds, that can (should) be increased if network bandwidth is low
in the openvas.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 10 seconds.
max_hosts
Number of hosts to test at the same time. It can be as low as you want it to be (obviously 1 is
the minimum)
max_checks
Number of checks to test at the same time 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 OpenVAS will
spawn max_hosts * max_checks processes.
drop_privileges
If this preference is set to 'yes', OpenVAS will attempt to drop its root privilege before
launching any VT and the new process owner is 'nobody'; the default value of this preference is
'no', meaning no change in behaviour.
nasl_drop_privileges_user
If a user is set, NASL functions can use this user to drop its root privilege. The new process
owner is set only for those process calling a nasl function which supports a drop privileges
action. This preference must not be mixed with 'drop_privileges'. If 'drop_privileges' is
enabled, this option should not be used, as 'drop_privileges' sets the owner to
vendor_version
Use the alternate vendor instead of the default one during scans.
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.
SEE ALSO
gvmd(8), gsad(8), ospd-openvas(8), openvas-nasl(1), openvas-nasl-lint(1), greenbone-nvt-sync(8)
MORE INFORMATION
The canonical places where you will find more information about OpenVAS are:
Community Portal
Development Platform
Traditional home site
AUTHORS
openvas was forked from nessusd in 2005. Nessusd was written by Renaud Deraison
<deraison@cvs.nessus.org>. Most new code since 2005 developed by Greenbone Networks GmbH.
Greenbone Vulnerability Management February 2021 OpenVAS(8)