2 - Raspberry PI Community Projects

possible, but if the web application was not up-to-date, chances are that the kernel and other
programs are outdated too; this sometimes follows a decision from the administrator who, despite
knowing about the vulnerability, neglected to upgrade the system since there are no local
users. The attacker can then take advantage of this second vulnerability to get root access.
VOCABULARY
Privilege escalation
This term covers anything that can be used to obtain more permissions than a
given user should normally have. The sudo program is designed for precisely
the purpose of giving administrative rights to some users. But the same term
is also used to describe the act of an aacker exploiting a vulnerability to
obtain undue rights.
Now the attacker owns the machine; they will usually try to keep this privileged access for as
long as possible. This involves installing a rootkit, a program that will replace some components
of the system so that the attacker will be able to obtain the administrator privileges again at a
later time; the rootkit also tries hiding its own existence as well as any traces of the intrusion.
A subverted ps program will omit to list some processes, netstat will not list some of the active
connections, and so on. Using the root permissions, the attacker was able to observe the
whole system, but didn't find important data; so they will try accessing other machines in the
corporate network. Analyzing the administrator's account and the history files, the attacker
finds what machines are routinely accessed. By replacing sudo or ssh with a subverted program,
the attacker can intercept some of the administrator's passwords, which they will use on
the detected servers… and the intrusion can propagate from then on.
This is a nightmare scenario which can be prevented by several measures. The next few sections
describe some of these measures.
14.5.3. Choosing the Soware Wisely
Once the potential security problems are known, they must be taken into account at each step of
the process of deploying a service, especially when choosing the software to install. Many web
sites, such as SecurityFocus.com, keep a list of recently-discovered vulnerabilities, which can
give an idea of a security track record before some particular software is deployed. Of course,
this information must be balanced against the popularity of said software: a more widely-used
program is a more tempting target, and it will be more closely scrutinized as a consequence. On
the other hand, a niche program may be full of security holes that never get publicized due to a
lack of interest in a security audit.
VOCABULARY
Security audit
A security audit is the process of thoroughly reading and analyzing the source
code of some soware, looking for potential security vulnerabilities it could
contain. Such audits are usually proactive and they are conducted to ensure
a program meets certain security requirements.
In the Free Software world, there is generally ample room for choice, and choosing one piece
of software over another should be a decision based on the criteria that apply locally. More
402 The Debian Administrator's Handbook