\begin{table*}[ht]
\begin{tabu} to 1\textwidth {X[l] X[l]}
\hline
\bf Assumptions of existing work & \bf Points of failure in a cloud environment\\
\hline
System is monitored continuously from power-on and throughout its lifecycle & VMs can be created, cloned, reverted to snapshots and migrated arbitrarily
throughout their lifetime. \\
\hline
Guest system is clean when it starts being monitored & VMs can come into existence already infected or compromised.\\
\hline
Guest system can be modified on the fly to insert
hooks or other monitoring mechanisms & Some customized systems may not be able to be modified, or we may not have
the knowledge necessary to do the modifications. \\
\hline
Guest OS is known in advance & VMs may be configured with any one or more guest OSes (e.g., multi-boot VMs). \\
\hline
Guest OS source code is available & Most real-world attacks (e.g. rootkits) operate on Windows. \\
\hline
Guest OS information (e.g. location of data structures)
is available & The location of internal data structures is unknown when no source code and no
version information are available. \\
\hline
Malware is known in advance and given as blacklists & New malware is created constantly, realistic protection cannot rely on blacklists. \\
\hline
Trusted boot process exists & Not all h/w platforms, hypervisors, and OSes support trusted boot. \\
\hline
\end{tabu}
\captionof{table}{ \bf Assumptions made by existing kernel integrity-checking mechanisms}
\captionsetup[table]{textfont={bf,large}}
\end{table*}