I am thinking about either a career in Network Security or in Machine Learning?

I'd say go with what you're most interested in, both of those choices are good ones from a getting hired perspective.

In general, if you're good at something, especially in computer science/IT, then you can get hired. And the key to getting good at something is to pick the subjects you're interested in. Machine learning is also a rapidly growing discipline right now.

Often students in technical educations severely underestimate how easy it will be for them to get a job after their studies. I believe this is largely the companies' fault. They often ignore the students up until the very end of the education when they suddenly start calling and trying to sign up the student as quickly as possible with the classical "exploding offer" (http://www.joelonsoftware.com/items/2008/11/26.html).

Hi Wenge,

I love to see people define their interests and pursue them with passion. Whatever you decide, you'll be most successful if you strive to perform every task with excellence.

My comments are reflective of a US based perspective, so they might not fit perfectly with opportunities in the UK.

There is considerable overlap between the disciplines of Networking and Artificial Intelligence; you may not need to select one technical path to the exclusion of the other. I suspect that your bigger decision is actually more basic... do you want to pursue your technology interests in an academic environment or in a commercial environment. Expertise in either discipline will typically require university level academic training, although it is definitely difficult to find an Artificial Intelligence job if you don't have a graduate degree.

My own career path required me to make a similar decision during my master's program in Computer Science. I selected an Artificial Intelligence emphasis, which led to employment with a group developing model based control systems. But I transitioned into network engineering work 20 years ago, and have absolutely loved working with data and voice networks ever since.

Academic research institutions, and the high end development labs of commercial companies (e.g. Google Labs), are where you'll find the cutting edge thinking about how to develop AI learning algorithms that detect network security violations and suspicious user behavior. Experience with "automatic heuristic creation" - a fancy way of describing the AI task of creating rules to describe what normal network activity looks like - is in demand for developers of commercial Intrusion Detection Systems (IDSs) and Intrusion Prevention Systems (IPSs). MITRE and Draper Labs are several commercial companies that function as academic research groups, with their security and AI groups generally focused on government funded research projects.

In the US, there are many network related job opportunities. Network security companies in particular are hiring network security technologists for a wide variety of positions requiring various levels of technical skill. While academic positions focus on intellectual research capability, the commercial environment provides technologists with broad employment opportunities in areas such as product development, product sales, and product support. Network Security Companies are growing, and new opportunities arise regularly.

If you're solely interested in finding employment and being paid for working as a technologist, then you'll find more employment opportunities with a background in network technology. This isn't to say that you shouldn't pursue Artificial Intelligence... that may be your passion and where you will find the opportunity that fits you best.

Whatever you decide, your best opportunities will arise if you learn the material thoroughly and strive for excellence.

Best Wishes,
Steve

I would challenge yourself future to think about what world problem would l like to solve....USING network security and/or machine Learning.  Also as a wise mentor told me one time, networks were meant to pass traffic, not do security.  So I would make sure you know what you really would like to do in the network field OR security field.  Machine Learning is still a single TOOL for solving problems within industry, so focus on finding your passion for a specific industry and then a passion for the problems that industry is having in helping mankind......then apply Machine Learning.  Good Luck.

Both are equally challenging..but you will have lot more fun in Machine learning. Today and in future. .With IOT coming up ..machine learning is a must skill to have..hope this helps