Deployment Security Best Practices

Nasuni Access Anywhere uses the Apache Web Server to serve pages and the underlying Linux Operating System is CentOS. CentOS is hardened using NSA hardening guidelines. You can review these at: http://www.nsa.gov/ia/mitigation_guidance/security_configuration_guides/operating_systems.shtml

Access Anywhere is also extensively tested using commercial penetration testing software prior to each major and minor release.

Access Anywhere can be extensively configured as required as the infrastructure software is industry standard and well understood .

We provide a separate white paper for High Availability guidelines. This white paper suggests some best practice but ultimately the deployment best practices are the responsibility of the deployer and should be inline with their existing deployment practices for such systems.

Access Anywhere is setup for integration with a customized version of Fail2Ban (http://www.fail2ban.org/). This is disabled by default but can be enabled by Access Anywhere Appliance Admin.

Fail2Ban is an intrusion prevention software framework that can help protect Access Anywhere from brute-force attacks.

Fail2Ban scans logs file for malicious patterns ie. DoS attacks, too many password failures, SSH logins, seeking exploits, trying to scan for download links etc. If the software detects such malicious patterns it automatically updates Access Anywhere firewall rules to reject IP addresses for a specified amount of time (10 minutes).

This is constantly working and scanning and as such it is an extra security protection for the appliance. Fail2Ban can also be setup to help prevent DOS attacks. To do this simply edit /etc/fail2ban/jail.conf and add the following to the end:

# Fail2Ban configuration file #
#
[Definition]
# Option: failregex
# Note:This regex will match any GET entry in your logs, so basically all valid and not valid entries are a match. # You should set up in the jail.conf file, the maxretry and findtime carefully in order to avoid false positives.
failregex = ^<HOST> -.*\"(GET|POST).*
# Option: ignoreregex
# Notes.: regex to ignore. If this regex matches, the line is ignored. #Values:TEXT
#
ignoreregex = ^<HOST> -.*\"(GET|POST).*Googlebot

The above will scan the logs and if it has more than 50 requests in 300 seconds, it will be banned. You can add to the exclude regex any line you do not want banned, for example here is place Google. To provide further information you can add some code in actionban to display extra information in an email.

actionban = printf %%b "Subject: [Fail2Ban] <name>: banned <ip> From: Fail2Ban <<sender>>
To:<dest>\n Hi,\n
The IP <ip> has just been banned by Fail2Ban after <failures> attempts against <name>.\n\n
Lines containing IP:<ip> in <logpath>\n `grep '\<<ip>\>' <logpath>`\n\n
Here are more information about <ip>:\n `/usr/bin/whois <ip>`\n
Regards,\n
Fail2Ban" | /usr/sbin/sendmail -f <sender> <dest>

This is an example of how Fail2Ban can be used to help prevent attacks but in an of itself it is not a solution. It is just one security measure that can be taken for protection.

There are many commercial services that can be used to protect an infrastructure from attacks. Many ISP's / MSP's and companies may already be using these.

Examples are:

https://www.cloudflare.com

http://www.dosarrest.com

http://www.blacklotus.net

http://blockdos.net

http://www.prolexic.com

Proxy Solutions can be used in front of Access Anywhere to provide an extra layer of protection against attacks (as well as High availability and load balancing) such as:

• DOS / DDOS attacks
• SYN Flood attacks
• Slow DOS (SlowLoris) attacks
• Script Abusers

There are a number of solutions that can be used here such as the open source Squid, HAProxy, and other commercial solutions.

HAProxy is a free, very fast and reliable solution offering high availability, load balancing, and proxying for TCP and HTTP-based applications. It is particularly suited for web sites which receive very high loads while needing persistence or Layer7 processing. HA Proxy can also be configured to help mitigate potential attacks.

If you are running your own Load Balancer based on HAProxy, look at the sysctl below (edit /etc/sysctl.conf with regards to mitigation of SYN Flood attacks. # Protection SYN flood net.ipv4.tcp_syncookies = 1 net.ipv4.conf.all.rp_filter = 1 net.ipv4.tcp_max_syn_backlog = 1024

Note: If the attack is very large and saturates internet bandwidth, the only solution is to ask the internet access provider to null route the attackers IPs on its core network.

For Slow DOS (SlowLoris) attacks clients will slowly send requests to a server, header by header, or character by character, waiting a long time between each of them and the server have to wait until the end of the request to process, and send back the response. The purpose of the attack is to prevent regular use of the service as the attacker is using all the available resources with these very slow requests. In order to protect against this kind of attack setup the HAProxy option timeout http-request€. It can set to 5s, which should be long enough. This simply tells HAProxy to give a 5 second time limit to a client to send its whole HTTP request, otherwise HAProxy will shut the connection with an error.

HAProxy can be quite a comprehensive solution as a defense for attacks and is in use in many companies and ISP's.

A good place for further information is: Use a Load Balancer as a First Row of Defense Against DDOS.

The mitigate host header injection attacks, Access Anywhere provides controls to set and control the hostname can be used for the appliance.

To force set the hostname, apply the following configuration:

ffconfig set hostname 'sme.example.com'

Two levels of brute force protection are available within Access Anywhere:

• General Brute Force Protection - automatically blocking any person successively failing to login to any account over a configurable number of times (Site Functionality)
• Account Specific Lock-Out - automatically suspending user accounts where a successive number of failed login attempts are made (Org Policies)

This section provides details on options that can be considered for protection against various internet attacks when deploying Access Anywhere.

Many Companies and ISP / MSP's may already have their own best practices and guidelines for such deployments and what is presented in this white paper can be considered and addendum to existing best practices for production deployment.

For a general security overview of the Access Anywhere software please visit the Security section of the Docs.