Cisco Blogs


Cisco Blog > Security

Using DNS RPZ to Block Malicious DNS Requests

October 2, 2013 at 10:00 am PST

After delivering several presentations at Cisco Live and Cisco Connect this year, I received a few questions regarding DNS Response Policy Zones (RPZ) and how can they be used to block DNS resolution to known malicious hosts and sites. I decided to write this short post to explain what it is and provide several pointers.

DNS RPZ is a technology developed by ISC available since Bind version 9.8. Network administrators can use DNS RPZ to essentially stop malware-infected hosts from reaching their command and control (C&C) servers by blocking DNS resolution to known malicious hosts and sites. This effectively turns a recursive DNS server into a DNS firewall. In fact, many people refer to DNS RPZ as the “DNS Firewall.” Various ISPs are testing and implementing this to provide additional protection to their customers.

Note: DNS RPZ will block DNS resolution, machines connecting to the C&C via IP address will not be blocked.

The following figure provides an overview of how DNS RPZ works.

RPZ-overview1

Read More »

Tags: , , , , , , , , ,

TMA? Get Some Relief from Acronym Overload

I see and hear a variety of acronyms being used on a daily basis. I recently heard one tossed around with good humor that makes a point: TMA or Too Many Acronyms. Every once in a while, when I think I’ve embedded the definition and use of an acronym into my long-term memory (anything beyond an extended weekend), it seems as if either a new acronym was spawned, or it has been overloaded with a different meaning. My goal in this blog post is offer both a refresher on some topical acronyms that appear to be quite commonly circulated in security technology circles and media outlets. It is challenging to be a subject matter expert in every aspect of cyber security. Whether you are reading an article, joining a conversation or preparing for a presentation or certification in the realm of cyber security, you may not be completely perplexed by these acronyms when you come across them and become more familiar with them. For situational purposes, I organized the acronyms into categories where I have seen them used frequently and included related links for each of them.

Network Infrastructure

AAAAuthentication, Authorization, and Accounting. This is a set of actions that enable you to control over who is allowed access to the network, what services they are allowed to use once they have access, and track the services and network resources being accessed.

ACL/tACL/iACL/VACL/PACLAccess Control List. ACLs are used to filter traffic based upon a set of rules that you define. For ACLs listed with a prefix (for example, t=transit, i=infrastructure, V=VLAN (Virtual Local Area Network), P=Port)), these ACLs have special purposes to address a particular need within the network.

FW/NGFW/FWSM/ASASM: Firewall/Next Generation Firewall/Firewall Service Module/Adaptive Security Appliance Services Module. These products provide a set of security features designed to govern the communications via the network. Cisco provides firewall features as a dedicated appliance or hardware module that can be added to a network device such as a router.

IPS: Intrusion Prevention System. Typically, this is a network appliance that is used to examine network traffic for the purposes of protecting against targeted attacks, malware, and application and operating system vulnerabilities. In order to ensure the effectiveness of a Cisco IPS device, it  should be maintained using Cisco’s IPS subscription service.

DNSSECDomain Name System (DNS) Security Extensions. That’s right, we have an acronym within an acronym. These are the specifications for security characteristics that make it possible to verify the authenticity of information stored in DNS. This validation makes it possible to provide assurances to resolvers that when they request a particular piece of information from the DNS, that they receive the correct information published by the authoritative source. Read More »

Tags: , , , , , , , , ,

Coordinated Attacks Against the U.S. Government and Banking Infrastructure

Prologue

On April 10, 2013, a collective of politically motivated hacktivists announced a round of planned attacks called #OPUSA. These attacks, slated to begin May 7, 2013, are to be launched against U.S.-based targets. #OPUSA is a follow-up to #OPISRAEL, which were a series of attacks carried out on April 7 against Israeli-based targets. Our goal here is to summarize and inform readers of resources, recommendations, network mitigations, and best practices that are available to prevent, mitigate, respond to, or dilute the effectiveness of these attacks. This blog was a collaborative effort between myself, Kevin TimmJoseph KarpenkoPanos Kampanakis, and the Cisco TRAC team.

Analysis

If the attackers follow the same patterns as previously witnessed during the #OPISRAEL attacks, then targets can expect a mixture of attacks. Major components of previous attacks consisted of denial of service attacks and web application exploits, ranging from advanced ad-hoc attempts to simple website defacements. In the past, attackers used such tools as LOICHOIC, and Slowloris.

Publicly announced attacks of this nature can have highly volatile credibility. In some cases, the announcements exist only for the purpose of gaining notoriety. In other cases, they are enhanced by increased publicity. Given the lack of specific details about participation or capabilities, the exact severity of the attack can’t be known until it (possibly) happens. Read More »

Tags: , , , , , , , , , , , , , , , , , , ,

I Can’t Keep Up with All These Cisco Security Advisories: Do I Have to Upgrade?

April 2, 2013 at 6:00 am PST

“A security advisory was just published! Should I hurry and upgrade all my Cisco devices now?”

This is a question that I am being asked by customers on a regular basis. In fact, I am also asked why there are so many security vulnerability advisories. To start with the second question: Cisco is committed to protecting customers by sharing critical security-related information in a very transparent way. Even if security vulnerabilities are found internally, the Cisco Product Security Incident Response Team (PSIRT) – which is my team – investigates, drives to resolution, and discloses such vulnerabilities. To quickly answer the first question, don’t panic, as you may not have to immediately upgrade your device. However, in this article I will discuss some of the guidelines and best practices for responding to Cisco security vulnerability reports.

Read More »

Tags: , , , , , , , , , , , ,

Targeted Attack, Targeted Response: Designing and Implementing an Incident Response Plan That Works

September 4, 2012 at 7:30 am PST

A few weeks ago I had the pleasure of participating, as a guest speaker, in a webinar titled “Targeted Attack, Targeted Response: Designing and Implementing an IR Plan That Works.” Joe Riggins, Senior Director of Incident Response for HBGary, moderated this Q&A format webinar. We discussed the current incident response (IR) challenges companies are facing, as well as specific steps organizations can take to design, test, and successfully implement an ongoing IR plan for their specific business environment.

The webinar recording can be accessed here.

Read More »

Tags: ,