diff --git a/Chapters/2.Background.tex b/Chapters/2.Background.tex
index 8567ce3..89a8f4c 100644
--- a/Chapters/2.Background.tex
+++ b/Chapters/2.Background.tex
@@ -1294,63 +1294,104 @@ migration and rollback attacks). Από την άλλη, όσον αφορά τ
 
 \begin{table}[!ht]
 \caption{Κατηγοριοποίηση απειλών στην εικονικοποίηση}
-\renewcommand{\arraystretch}{1.5}
+\renewcommand{\arraystretch}{1.3}
+\aboverulesep=-0.1ex
+\belowrulesep=-0.1ex
 \centering
 \newcolumntype{C}{>{\centering\arraybackslash}m{6cm}}
-\newcommand\Tstrut{\rule{0pt}{2.6ex}}         % = `top' strut
-\newcommand\Bstrut{\rule[-0.9ex]{0pt}{0pt}}   % = `bottom' strut
 \textgreek{\begin{tabular}{||C|C||}
 \hline
-
-Κατηγορία & Απειλές και πιθανά ευπαθή σημεία \\ [0.5ex]
-
-\hline\hline
-
-Απειλές Δικτύου &
-
-XML Signature Wrapping Attacks\Tstrut\Bstrut\hline
-Flooding Attacks (DDoS)\Tstrut\Bstrut\hline
-Metadata Spoofing Attacks\Tstrut\Bstrut\hline
-Insecure Web Apps \& APIs\Tstrut\Bstrut\hline
-Cross Site Scripting Attacks\Tstrut\Bstrut\hline
-Port scanning\Tstrut\Bstrut\hline
-Botnets\Tstrut\Bstrut\hline
-Spoofing attacks\Tstrut\Bstrut\hline
-DNS attacks\Tstrut\Bstrut\hline
-Sniffer attacks\Tstrut\Bstrut\hline
-Denial of Service (DoS)\Tstrut\Bstrut \\
-
-\hline
-
-Απειλές για τον Πάροχο &
-
-Sniffing Attacks\Tstrut\Bstrut\hline
-Spoofing Attacks\Tstrut\Bstrut\hline
-Denial of Service Attacks\Tstrut\Bstrut\hline
-cross VM side channel attacks\Tstrut\Bstrut\hline
-VM scheduler based attacks\Tstrut\Bstrut\hline
-VM Hopping\Tstrut\Bstrut\hline
-VM Escape\Tstrut\Bstrut\hline
-Dynamic Data Updates\Tstrut\Bstrut\hline
-Data scavenging\Tstrut\Bstrut \\
-
-\hline
-
-Απειλές για τις Εφαρμογές &
-
-Malware injection\Tstrut\Bstrut\hline
-Steganography attacks\Tstrut\Bstrut\hline
-Web services attacks\Tstrut\Bstrut\hline
-Protocol-based attacks\Tstrut\Bstrut\hline
-Security Misconfigurations\Tstrut\Bstrut\hline
-SQL Injection Attacks\Tstrut\Bstrut \\
-
-\hline
+                       Κατηγορία                 & Απειλές και πιθανά ευπαθή σημεία  \\ \hline\hline
+\multirow{11}{*}{\hfil Απειλές Δικτύου}          & XML Signature Wrapping Attacks    \\ \cmidrule(lr){2-2}
+                                                 & Flooding Attacks (DDoS)           \\ \cmidrule(lr){2-2}
+                                                 & Metadata Spoofing Attacks         \\ \cmidrule(lr){2-2}
+                                                 & Insecure Web Apps \& APIs         \\ \cmidrule(lr){2-2}
+                                                 & Cross Site Scripting Attacks      \\ \cmidrule(lr){2-2}
+                                                 & Port scanning                     \\ \cmidrule(lr){2-2}
+                                                 & Botnets                           \\ \cmidrule(lr){2-2}
+                                                 & Spoofing attacks                  \\ \cmidrule(lr){2-2}
+                                                 & DNS attacks                       \\ \cmidrule(lr){2-2}
+                                                 & Sniffer attacks                   \\ \cmidrule(lr){2-2}
+                                                 & Denial of Service (DoS)           \\ \hline
+\multirow{9}{*}{\hfil Απειλές για τον Πάροχο}    & Sniffing Attacks                  \\ \cmidrule(lr){2-2}
+                                                 & Spoofing Attacks                  \\ \cmidrule(lr){2-2}
+                                                 & Denial of Service Attacks         \\ \cmidrule(lr){2-2}
+                                                 & cross VM side channel attacks     \\ \cmidrule(lr){2-2}
+                                                 & VM scheduler based attacks        \\ \cmidrule(lr){2-2}
+                                                 & VM Hopping                        \\ \cmidrule(lr){2-2}
+                                                 & VM Escape                         \\ \cmidrule(lr){2-2}
+                                                 & Dynamic Data Updates              \\ \cmidrule(lr){2-2}
+                                                 & Data scavenging                   \\ \hline
+\multirow{6}{*}{\hfil Απειλές για τις Εφαρμογές} & Malware injection                 \\ \cmidrule(lr){2-2}
+                                                 & Steganography attacks             \\ \cmidrule(lr){2-2}
+                                                 & Web services attacks              \\ \cmidrule(lr){2-2}
+                                                 & Protocol-based attacks            \\ \cmidrule(lr){2-2}
+                                                 & Security Misconfigurations        \\ \cmidrule(lr){2-2}
+                                                 & SQL Injection Attacks             \\ \hline
 \end{tabular}}
 \label{table:virtualizationThreatCategories}
 \renewcommand{\arraystretch}{1}
 \end{table}
 
+% \begin{table}[!ht]
+% \caption{Κατηγοριοποίηση απειλών στην εικονικοποίηση}
+% \renewcommand{\arraystretch}{1.5}
+% \centering
+% \newcolumntype{C}{>{\centering\arraybackslash}m{6cm}}
+% \newcommand\Tstrut{\rule{0pt}{2.6ex}}         % = `top' strut
+% \newcommand\Bstrut{\rule[-0.9ex]{0pt}{0pt}}   % = `bottom' strut
+% \textgreek{\begin{tabular}{||C|C||}
+% \hline
+% %
+% Κατηγορία & Απειλές και πιθανά ευπαθή σημεία \\ [0.5ex]
+% %
+% \hline\hline
+% %
+% Απειλές Δικτύου &
+% %
+% XML Signature Wrapping Attacks\Tstrut\Bstrut\hline
+% Flooding Attacks (DDoS)\Tstrut\Bstrut\hline
+% Metadata Spoofing Attacks\Tstrut\Bstrut\hline
+% Insecure Web Apps \& APIs\Tstrut\Bstrut\hline
+% Cross Site Scripting Attacks\Tstrut\Bstrut\hline
+% Port scanning\Tstrut\Bstrut\hline
+% Botnets\Tstrut\Bstrut\hline
+% Spoofing attacks\Tstrut\Bstrut\hline
+% DNS attacks\Tstrut\Bstrut\hline
+% Sniffer attacks\Tstrut\Bstrut\hline
+% Denial of Service (DoS)\Tstrut\Bstrut \\
+% %
+% \hline
+% %
+% Απειλές για τον Πάροχο &
+% %
+% Sniffing Attacks\Tstrut\Bstrut\hline
+% Spoofing Attacks\Tstrut\Bstrut\hline
+% Denial of Service Attacks\Tstrut\Bstrut\hline
+% cross VM side channel attacks\Tstrut\Bstrut\hline
+% VM scheduler based attacks\Tstrut\Bstrut\hline
+% VM Hopping\Tstrut\Bstrut\hline
+% VM Escape\Tstrut\Bstrut\hline
+% Dynamic Data Updates\Tstrut\Bstrut\hline
+% Data scavenging\Tstrut\Bstrut \\
+% %
+% \hline
+% %
+% Απειλές για τις Εφαρμογές &
+% %
+% Malware injection\Tstrut\Bstrut\hline
+% Steganography attacks\Tstrut\Bstrut\hline
+% Web services attacks\Tstrut\Bstrut\hline
+% Protocol-based attacks\Tstrut\Bstrut\hline
+% Security Misconfigurations\Tstrut\Bstrut\hline
+% SQL Injection Attacks\Tstrut\Bstrut \\
+% %
+% \hline
+% \end{tabular}}
+% \label{table:virtualizationThreatCategories}
+% \renewcommand{\arraystretch}{1}
+% \end{table}
+
 \clearpage
 
 Κατηγοριοποίηση με μεγαλύτερη λεπτομέρεια ως προς τις κατηγορίες αδυναμιών όπου