diff --git a/pdf/51. Firewalls and Internet Security.pdf b/pdf/51. Firewalls and Internet Security.pdf new file mode 100644 index 0000000..cfc0fad Binary files /dev/null and b/pdf/51. Firewalls and Internet Security.pdf differ diff --git a/pdf/52. An Introduction To Computer Security - The NIST Handbook.pdf b/pdf/52. An Introduction To Computer Security - The NIST Handbook.pdf new file mode 100644 index 0000000..1b12517 Binary files /dev/null and b/pdf/52. An Introduction To Computer Security - The NIST Handbook.pdf differ diff --git a/pdf/53. Unauthorized Access - Physical Penetration Testing for IT Security Teams.pdf b/pdf/53. Unauthorized Access - Physical Penetration Testing for IT Security Teams.pdf new file mode 100644 index 0000000..2efefa2 Binary files /dev/null and b/pdf/53. Unauthorized Access - Physical Penetration Testing for IT Security Teams.pdf differ diff --git a/pdf/54. Testing Web Security.pdf b/pdf/54. Testing Web Security.pdf new file mode 100644 index 0000000..627e859 Binary files /dev/null and b/pdf/54. Testing Web Security.pdf differ diff --git a/pdf/55. Maximum Security - A Hacker's Guide to Protecting Your Internet Site and Network.pdf b/pdf/55. Maximum Security - A Hacker's Guide to Protecting Your Internet Site and Network.pdf new file mode 100644 index 0000000..5006f75 Binary files /dev/null and b/pdf/55. Maximum Security - A Hacker's Guide to Protecting Your Internet Site and Network.pdf differ