Having played both the attacker and defender role for many years something I have often seen and even done myself is make statements and assumptions about the "sophistication" of my adversary.
Often when some big hack occurs, blogs, media stories and quotes from experts will espouse opinions that "the attacker was not very sophisticated" or "it was an extremely sophisticated attack". I believe that often times, and I myself have been guilty of this, these assertions are the result of a wrong headed analysis and misunderstanding of what sophistication means in the context of computer attacks.
An example will help illustrate the point. I have heard stuxnet labeled both sophisticated and unsophisticated. One might be tempted to point to the inclusion of 4 0days as proving that highly skilled attackers launched this attack. Well 0days can be bought. Others might say; well the way it was caught and the fact that it could infect more than it's presumed target means the attackers weren't very good. Even the most well developed attacks get caught eventually. (See the device the Russians implanted in the Great Seal 60 years ago)
A truly sophisticated attacker will use only what is necessary and cost effective to achieve their goals and no more. An even better attacker will attempt to convince you they are not very good and waste as much of your time as possible while still achieving the goal.
I would put forth the idea that the determination of sophistication be based on the following:
Did the attacker achieve their goals?
Let us assume further that these goals consist of:
1.) Gaining unauthorized access to one or more of your systems
If they achieve #1 then they have already proven to be more sophisticated than your first line of defensive / prevention system as well as your user awareness and training program.To speak of the attacker as unsophisticated because they used an automated SQL injection tool or basic phishing email is silly because you have no idea how good they are based soley on the penetration mechanism and they are already more sophisticated than your ability to stop them.
2.) Evasion of detection, at least for the period of time required to complete some goals
If they have a shell on one of your systems, and nothing detects, alerts or responds, then the attacker is more sophisticated than your SIM implementation, IDS and first line analysts at least from the detection during initial attack standpoint. The fact that they used XOR vs full SSL to protect network communications from detection is irrelevant and gives you no clue as to how good they are.
3.) Access to and/or exfiltration of sensitive data
If the attacker has been able to take the data they are targeting then they have overcome your internal controls, ACLs and data protection. It matters not if they used a zip file or steganography to package the data.
If the attacker can persist with unauthorized access on your system for any period of time then they have outsmarted your defensive team, your secure configuration management and basically all your defenses. It doesn't matter if their method of persistence is a simple userland executable launched from the Run key in the registry or a highly stealthy kernel driver, they won that round.
If they can cause a real world effect such as blowing up your centrifuges, gaining a competitive advantage, or spending your money then that is the final nail in your coffin. They are more sophisticated than you are, regardless of what type of exploit they used, if it was a 10 year old PERL CGI bug or one that uses memory tai chi to elegantly overcome windows 7 buffer overflow protection.
Lets think about this for a minute. Think of all the money, time, resources and personel you have expended on perimeter defense, detection and alerting, and analytical teams. Think of the work involved at the vendors who have developed all of the products and appliances you have purchased. The PHDs at AV vendors designing heuristics, the smart guys and girls developing exploits and signatures at your favorite IDS company. The awesome hax0rs at the pen test company you just hired. The often millions of dollars spent on defense.
All of this and the attacker has subverted it, maybe with a month of work, maybe less, and considerably less funding in most cases. So who is the sophisticated one?
The only place you might have won is in the forensics post-event department, usually the least funded and most resource starved component of your program. This is usually where the determination is made that the attacker was not very sophisticated because it was possible to reverse engineer the attack and understand the tools and techniques used. That's great but just because you an understand that an assasin used a rock to kill a VIP doesn't mean the assasin sucks if they got away from the highly skilled protection detail, the target is dead, and their identity remains unknown.
So pause for a moment before you label an attacker unsophisticated or a skript kiddie. Ask yourself, did they achieve the above mentioned goas? If so then they outsmarted you.