Читать книгу Alice and Bob Learn Application Security - Tanya Janca - Страница 17

Every part of your software can be attacked; each feature, input, page, or button. The smaller your application, the smaller the attack surface. If you have four pages with 10 functions versus 20 pages and 100 functions, that’s a much smaller attack surface. Every part of your app that could be potentially exposed to an attacker is considered attack surface.

Attack surface reduction means removing anything from your application that is unrequired. For instance, a feature that is not fully implemented but you have the button grayed out, would be an ideal place to start for a malicious actor because it’s not fully tested or hardened yet. Instead, you should remove this code before publishing it to production and wait until it’s finished to publish it. Even if it’s hidden, that’s not enough; reduce your attack surface by removing that part of your code.

TIP Legacy software often has very large amounts of functionality that is not used. Removing features that are not in use is an excellent way to reduce your attack surface.

If you recall from earlier in the chapter, Alice and Bob both have medical implants, a device to measure insulin for Alice and a pacemaker for Bob. Both of their devices are “smart,” meaning they can connect to them via their smart phones. Alice’s device works over Bluetooth and Bob’s works over Wi-Fi. One way for them to reduce the attack surface of their medical devices would have been to not have gotten smart devices in the first place. However, it’s too late for that in this example. Instead, Alice could disable her insulin measuring device’s Bluetooth “discoverable” setting, and Bob could hide the SSID of his pacemaker, rather than broadcasting it.