Local Area Networks (LANs) in Aircraft - FTP Directory Listing - FAA

if an attacker resets a Unix device’s time to a week from now, then it will trigger logrotate to
rotate the Unix logging files. If the attacker does this five times, then the current Unix syslog
files will be deleted, thereby eliminating the attacker’s tracks from the attacked device’s logging
system.
A.2.9 DATA DRIVEN ATTACKS.
These are perhaps the best-known mechanisms for cracking remote systems. Data driven attacks
are executed by sending data to an active service that causes unintended or undesirable results.
These types of attack include:
• Buffer Overflow attacks. A buffer overflow occurs when a user or process attempts to
place more data into a buffer (e.g., fixed array) than was originally allocated. A buffer
overflow condition normally causes a segmentation violation to occur. This event can be
potentially exploited to gain access to the target system. For example, if the process
where the buffer overflow occurred is running as root (e.g., is a communications
protocol), and if (at the appropriate place within the overflowing data) the data contained
code that executed the command /bin/sh, then /bin/sh would be executed with root
permissions, thereby giving the attacker a shell (e.g., command lines) to use that has root
permissions. In this manner, attackers can gain control of OSs. Once they have gained
control, they can establish backdoors and Trojan horses for subsequent access.
Safeguards against buffer overflow attacks include improved software development
practices. For example, validating arguments within code; using more secure routines
such as (for the C programming language) fget(), strncpy() and strncat(); better test and
audit practices; and using safe compilers such as Immunix’s StackGuard or Janus.
Alternatively, rather than recompiling every program on the system, the Libsafe dynamic
library file can be installed with either the environment variable $LD_PRELOAD
specified or else list it in /etc/ld.so.preload. Unfortunately, these types of vulnerabilities
only reduce the number of buffer overflows without eliminating all of them. Thus, this
threat continues to exist even within systems whose developers have undertaken these
types of safeguards.
• Input Validation attacks. An input validation attack leverages a programming flaw where
(1) the program fails to properly parse and validate received input; (2) a module accepts
this syntactically incorrect input; (3) the module fails to handle the missing input fields;
and (4) a field value correlation error subsequently occurs. If a program accepts usersupplied
input and did not properly validate it, it could be tricked into executing arbitrary
code via leveraging Unix shell escape commands. Executing nonvalidated escape
sequences provide a comparable capability to the attacker to crack the device as buffer
overflows. The primary safeguard against this type of problem is improved software
development practices.
These classes of attacks point out the importance of shell access within Unix systems. Within
these OSs, shells provide command line capabilities to remote or local users. A successful
logon, regardless of whether it is local or remote, results in the user receiving a shell. Once the
user has a shell, then he or she is able to perform any function on that computer that he or she is
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