#krackattack WiFi encryption “Key Reinstallation Attack”

What happened?

A flaw has been discovered and widely reported as breaking WiFi encryption. The attack is a client-based attack and exploits vulnerabilities in the 4-way handshake of the WPA/2 protocol.

As the problem lies within the WiFi standard, the potential impact is widespread, affecting just about every smartphone and PC. The exploit could allow attackers to read WiFi traffic between devices and wireless access points. Certain implementations on Linux and Android devices are more severely impacted, allowing attackers to modify network traffic.

No need to panic

The flaw is not as ubiquitous and severe as the headlines suggest. The following context has been made public:

• Secured protocols (for example, HTTPS) still provide protection for applications.
• Attackers require close proximity to the wireless network – they need to be in range of the WiFi client.
• The attack is complex to execute and there are no public exploit tools currently available to facilitate the exploit (though this will likely change soon!).
• The exploit was responsibly disclosed, so vendors have already released patches (Microsoft) or intend to release soon (Android, Apple).

What can you do?

1) Implement patches when released.
2) Encrypt critical data in motion, independent of the network.
3) Ensure encryption is properly implemented to good standards (don’t invent your own!).
4) Use a virtual private network (VPN) solution on your devices, especially on public WiFi hotspots.
5) Advise users to only access secure sites, with https:// instead of http:// at the start of the address and check for a locked padlock or key in the browser address bar.

If you’re worried about the protection of your sensitive information, ask us how we can help.

Essential info on the “Essential 8”

A few days ago the Australian Signals Directorate released the new version of their document Strategies to Mitigate Cyber Security Incidents. This is the third version of this excellent guide and there are a number of obvious changes from the previous version in 2014. This year (unlike the 2014 release) ASD have chosen not to provide a summary of the key changes, so I did a quick side-by-side comparison. This post summarises the changes.

The obvious changes

There are three significant changes that have been made to this version of the document:

  1. The Top 4 is still around (and mostly the same), but now we also have the Essential 8
  2. The previous “Top 35” list of strategies is now grouped into strategies for: prevention of malware delivery and execution, limiting the extent of cyber security incidents, detecting cyber security incidents, recovering data and system availability, and preventing malicious insiders.
  3. The title has changed. The 2014 release was titled “Strategies to Mitigate Targeted Cyber Intrusions” – the new version is “Strategies to Mitigate Cyber Security Incidents”

My take on these high level changes is that the ASD seems to be aiming for the guidelines to be more widely applicable. Instead of just talking about targeted attacks, the advice is now more relevant to a wider range of cyber security incidents.
With a more cynical hat on, perhaps they are also coming to accept that no amount of guidance is going to be truly effective in preventing a targeted cyber intrusion from a well-resourced adversary.

What’s gone

The following items from the Top 35 list no longer seem to be present:

  • 19 – Web domain whitelisting for all domains
  • 32 – Block attempts to access websites by their IP address
  • 34 – Gateway blacklisting

These seem to be fair exclusions. Web domain whitelisting is a nice idea in theory, but invasive and difficult to maintain. Blocking attempts to access websites by IP address never really seemed like it would make much difference – getting a DNS record for a C&C server is hardly a difficult task.

What’s changed

The following strategies have been significantly changed, updated or merged:

  • The previous guidance / intent of “Workstation inspection of Microsoft Office files” (29) has been transformed into a new (better) strategy for protecting against malicious Office files – “Configure Microsoft Office macro settings”
  • The previous guidance for “Workstation and server configuration management” (21) has been given a more general heading of “Operating system hardening”. This new strategy also incorporates previous guidance for “Restrict access to Server Message Block (SMB) and NetBIOS” (27).
  • “Enforce a strong passphrase policy” (25) is now incorporated into a much broader “Protect authentication credentials”.
  • The verbosely-titled strategies “Centralised and time-synchronised logging of successful and failed computer events” (15) and “Centralised and time-synchronised logging of allowed and blocked network activity” (16) have been rolled up into “Continuous incident detection and response”
  • Elements of “Centralised and time-synchronised logging of successful and failed computer events” (15) have also made their way into the new strategy for “Endpoint detection and response software”.

These updates, changes and merges all seem to make a lot of sense. Personally, I would have taken this even further – I think there are more opportunities to reduce the overall number of strategies by rolling-up similar or related guidance. For example, in the strategies to prevent malware delivery and execution section we have “User application hardening” and “Configure Microsoft Office macro settings” – I would argue that the latter is a subset of the former.

What’s new

Perhaps the most interesting aspect of this year’s version of the document are the new entries to the list:

  • “Hunt to discover incidents” (Mitigation strategies to prevent malware delivery and execution). This is an excellent recommendation, and it is almost baffling that this wasn’t explicitly required in previous years.
  • “Personnel management” (Mitigation strategy specific to preventing malicious insiders)

And the following three new entries under “Mitigation strategies to recover data and system availability”:

  • “Daily backups”
  • “Business continuity and disaster recovery plans”
  • “System recovery capabilities”

These last three really underline ASD’s apparent change in thinking for this year’s release – instead of just being about ‘keeping the bad guys out’, this new guide better aligns to a ‘Prevent – Detect – Respond – Recover’ incident response approach.

Closing thoughts

  1. It is great that ASD produce this guide and make it publicly available. I believe that the guidance is sound and mostly I would agree with the assigned ratings for effectiveness, impact, cost, etc.
  2. I am not a huge fan of the new groupings for the strategies. I think that this may be confusing for casual readers and non-industry types. I am concerned that a customer might work their way down the “prevent” list from top to bottom, while completely ignoring the essential strategies from “limit” and “detect”. It would be nice for ASD to release the recommendations in a format that facilitated sorting by different attributes.
  3. It is good to see the guidance updated in a way that addresses changes to the threat landscape, changes to current attack patterns, changes to defensive technologies (and technology capabilities).

Bash bug will leave you shell shocked.

A vulnerability has been found in the Bash Unix shell. The vulnerability arises from a bug in the way that Bash processes environment variables. If an attacker is able to pass environment variable content to a network service that calls bash, they may be able to achieve arbitrary remote code execution on the target system.

This has potentially severe implications for any network service that runs bash as an interpreter.

  • CGI scripts on web servers can be leveraged to achieve remote code execution through HTTP requests.
  • Systems running SSH may also be vulnerable. By leveraging AcceptEnv, TERM or SSH_ORIGINAL_COMMAND environment variables, remote code execution may be achieved on affected systems.
  • Other network services may also be impacted (e.g. SMTP servers)

This has widespread severe security implications, as potentially any Linux/Unix system can be compromised remotely.

WHAT CAN YOU DO:

  • Upgrade bash on all Linux/Unix systems immediately
  • Temporarily firewall any Internet-facing SSH servers or web servers running shell-based CGI scripts until the bash patch can be applied.
  • For appliances, software appliances and embedded systems, contact the vendor to seek advice about patching.
  • Cry softly into your pillow
  • Run away from your job
  • Hit the pub.

More to follow…