John Marrett

John is Stack8's Director of Managed Services. John specializes in network and security, by developing innovative solutions for our clients and providing them with ongoing support.

Recent Posts

Microsoft Secure LDAP Security Update for Cisco UC Systems and SMACS

Posted by John Marrett on Feb 13, 2020 10:29:53 AM

Over the coming months, Microsoft will be publishing security updates related to Advisory ADV190023 that will significantly affect how LDAP can be used in a Microsoft Active Directory (AD) environment. In the first round of security patches scheduled for March 2020, logging will be enabled by default for insecure LDAP connections. In the second half of 2020 (so no earlier than July), insecure LDAP communications will be blocked. This will affect all external systems that make use of LDAP to synchronize and authenticate users.

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Topics: LDAP security, Microsoft Secure LDAP Security Update

CDPwn Vulnerabilities

Posted by John Marrett on Feb 6, 2020 9:13:26 AM

Today a collection of five vulnerabilities affecting Cisco phones and switches has been published. These vulnerabilities, identified collectively as CDPwn by Armis, the security firm that discovered them present a significant risk in many enterprise environments. For most enterprise customers, the vulnerabilities affecting phones (CVE-2020-3111) and switches running NX-OS (CVE-2020-3119  and CVE-2020-3120) are the principle areas of concern.

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Topics: CDPwn Vulnerabilities

Quick Bulk Changes with ciscocmd

Posted by John Marrett on Oct 24, 2019 6:00:00 AM

In the past, we've written about the device inventory techniques. I've spoken about device configuration management. Here's a video of my talk on the subject. Eric Lavoie, another member of our senior staff, spoke to me recently about needing to make a small change on 81 voice gateways. He was shocked by my casual estimate of the amount of time required to write the code to collect, validate, and correct the configuration. He went back to his desk, convinced there was an easier way to make the change, and he found one!

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Topics: ciscocmd

Troubleshooting PSTN Behaviour by Comparing Call Recordings and Packet Captures

Posted by John Marrett on Apr 11, 2019 11:30:52 AM

Your companies telecommunications are only as good as your voice quality. Without good voice quality... well there's always email.

Sometimes after you've corrected QoS misconfigurations, validated WAN and LAN behavior and validated your fixes you still have user complaints. In this blog post, we dive deep into techniques that allow you to analyze and measure the behavior of the PSTN, beyond your SIP termination points and into the public phone networks. In this specific example even call recordings showed good voice quality. However, we established that the issues were related to call latency. Normally there is no way to measure latency without the use of specialized tooling, but we developed the following technique.

There are a number of factors that contribute to poor voice quality. In this article, we discuss methods to troubleshoot and isolate voice quality issues outside of the network and on the PSTN using packet captures and call recordings. Packet captures are one of the most powerful troubleshooting tools we have.

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Topics: CUCM, Cisco CUCM, packet captures, Voice quality, PSTN

Enumerating Cisco ASA systems affected by CVE-2018-0101 using Shodan

Posted by John Marrett on Feb 5, 2018 1:43:57 PM

By now you've almost certainly heard about CVE-2018-0101, an unauthenticated, remote code execution vulnerability affecting Cisco ASAs. If you haven't, you should start planning to apply the update immediately to the ASAs in your environment. This vulnerability affects all ASAs that are configured to handle AnyConnect or clientless VPN connections. Some initial discussion in the security groups suggested that only clientless VPN was affected however this is not the case.

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Topics: CVE-2018-0101, Shodan, ASA

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