Security often lives in one of two states. It’s either something “I” take care of, because my organization is so small there isn’t anyone else taking care of it. Or it’s something those folks sitting over there in the corner take care of because the organization is, in fact, large enough to have a separate security team. In both cases, however, security is something that is done to networks, or something thought about kind-of off on its own in relation to networks.
I’ve been trying to think of ways to challenge this way of thinking for many years—a long time ago, in a universe far away, I created and gave a presentation on network security at Cisco Live (raise your hand if you’re old enough to have seen this presentation!).
If you haven’t found the trade-offs, you haven’t looked hard enough.
A perfect illustration is the research paper under review, Securing Linux with a Faster and Scalable Iptables. Before diving into the paper, however, some background might be good. Consider the situation where you want to filter traffic being transmitted to and by a virtual workload of some kind, as shown below.
To move a packet from the user space into the kernel, the packet itself must be copied into some form of memory that processes on “both sides of the divide” can read, then the entire state of the process (memory, stack, program execution point, etc.) must be pushed into a local memory space (stack), and control transferred to the kernel. This all takes time and power, of course.
One of the recurring myths of IPv6 is its very large address space somehow confers a higher degree of security. The theory goes something like this: there is so much more of the IPv6 address space to test in order to find out what is connected to the network, it would take too long to scan the entire space looking for devices. The first problem with this myth is it simply is not true—it is quite possible to scan the entire IPv6 address space rather quickly, probing enough addresses to perform a tree-based search to find attached devices. The second problem is this assumes the only modes of attack available in IPv4 will directly carry across to IPv6. But every protocol has its own set of tradeoffs, and therefore its own set of attack surfaces.
There is a rising tide of security breaches. There is an even faster rising tide of hysteria over the ostensible reason for these breaches, namely the deficient state of our information infrastructure. Yet the world is doing remarkably well overall, and has not suffered any of the oft-threatened giant digital catastrophes. Andrew Odlyzko joins Tom Ammon and I to talk about cyber insecurity.
Fastnetmon began life as an open source DDoS detection tool, but has grown in scope over time. By connecting Fastnetmon to open source BGP implementations, operators can take action when a denial of service event is detected, triggering black holes and changing route preferences. Pavel Odintsov joins us to talk about this interesting and useful open source project.
Backscatter is often used to detect various kinds of attacks, but how does it work? The paper under review today, Who Knocks at the IPv6 Door, explains backscatter usage in IPv4, and examines how effectively this technique might be used to detect scanning of IPv6 addresses, as well. Scanning the IPv6 address space is much more difficult because there are 2128 addresses rather than 232. The paper under review here is one of the first attempts to understand backscatter in the IPv6 address space, which can lead to a better understanding of the ways in which IPv6 scanners are optimizing their search through the larger address space, and also to begin understanding how backscatter can be used in IPv6 for many of the same purposes as it is in IPv4.
Kensuke Fukuda and John Heidemann. 2018. Who Knocks at the IPv6 Door?: Detecting IPv6 Scanning. In Proceedings of the Internet Measurement Conference 2018 (IMC ’18). ACM, New York, NY, USA, 231-237. DOI: https://doi.org/10.1145/3278532.3278553
When a recursive resolver receives a query from a host, it will first consult any local cache to discover if it has the information required to resolve the query. If it does not, it will begin with the rightmost section of the domain name, the Top Level Domain (TLD), moving left through each section of the Fully Qualified Domain Name (FQDN), in order to find an IP address to return to the host, as shown in the diagram below.
This is pretty simple at its most basic level, of course—virtually every network engineer in the world understands this process (and if you don’t, you should enroll in my How the Internet Really Works webinar the next time it is offered!). The question almost no-one ever asks, however, is: what, precisely, is the recursive server sending to the root, TLD, and authoritative servers?
A long time ago, I worked in a secure facility. I won’t disclose the facility; I’m certain it no longer exists, and the people who designed the system I’m about to describe are probably long retired. Soon after being transferred into this organization, someone noted I needed to be trained on how to change the cipher door locks. We gathered up a ladder, placed the ladder just outside the door to the secure facility, popped open one of the tiles on the drop ceiling, and opened a small metal box with a standard, low security key. Inside this box was a jumper board that set the combination for the secure door.
First lesson of security: there is (almost) always a back door.
I was reminded of this while reading a paper recently published about a backdoor attack on certificate authorities. There are, according to the paper, around 130 commercial Certificate Authorities (CAs). Each of these CAs issue widely trusted certificates used for everything from TLS to secure web browsing sessions to RPKI certificates used to validate route origination information. When you encounter these certificates, you assume at least two things: the private key in the public/private key pair has not been compromised, and the person who claims to own the key is really the person you are talking to. The first of these two can come under attack through data breaches. The second is the topic of the paper in question.
How do CAs validate the person asking for a certificate actually is who they claim to be? Do they work for the organization they are obtaining a certificate for? Are they the “right person” within that organization to ask for a certificate? Shy of having a personal relationship with the person who initiates the certificate request, how can the CA validate who this person is and if they are authorized to make this request?
Privacy problems are an area of wide concern for individual users of the Internet—but what about network operators? In this issue of The Internet Protocol Journal, Geoff Huston has an article up about privacy in DNS, and the various attempts to make DNS private on the part of the IETF—the result can be summarized with this long, but entertaining, quote:
The Internet is largely dominated, and indeed driven, by surveillance, and pervasive monitoring is a feature of this network, not a bug. Indeed, perhaps the only debate left today is one over the respective merits and risks of surveillance undertaken by private actors and surveillance by state-sponsored actors. … We have come a very long way from this lofty moral stance on personal privacy into a somewhat tawdry and corrupted digital world, where “do no evil!” has become “don’t get caught!”
Before diving into a full-blown look at the many problems with DNS security, it is worth considering what kinds of information can leak through the DNS system. Let’s ignore the recent discovery that DNS queries can be used to exfiltrate data; instead, let’s look at more mundane data leakage from DNS queries.