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No surprise with number 1. Number 9 may be a surprise to many.

TIOBE tracks the popularity of programming languages. Note that the rating is not about unveiling the ‘most superior’ programming language.

The rating is based on number of skilled engineers and search engine stats.

Number 1 is no surprise. It is Java. Note that Android’s success has got lot to with Java’s re-emergence (Java is the official language for Android development). So, I’m guessing it is tough for C to catch up to Java from now on.

Number 9 is Perl. Coming from Unix Administrator background, I see why this is the case. Countless tools and ad-hoc scripts are written in PERL in the Unix world. While it not the prettiest out there, PERL is not going away any time soon.

And by the way, if you have any doubts whether or not to learn python, you can stop doubting and start learning.

Here is the complete list:

Source: http://www.tiobe.com/index.php/content/paperinfo/tpci/index.html

A very useful function in SQL is ‘datepart’ which can be used to retrieve a particular part (such as day, month etc) from a date/time field.

For example, let us say you need to retrieve the count of all records from a table by date.

Select datepart(day,timestamp),count(*) from my_Log with (nolock)

Where status = ‘ERROR’

Group by datepart(day,log_date)

In the above query:

My_log: Table name

Log_date: column that is of date/time type

Here is all the ‘datepart’ you can use:

year

quarter

month

dayofyear

day

week

weekday

hour

minute

second

millisecond

microsecond

nanosecond

TZoffset

ISO_WEEK

There are several types of Network Security Attacks as described below:

1. SYN Flood
   

   Here the attacker sends a SYN request from a spoofed source address. When the server responds with SYN-ACK, the source never replies back leaving the server handing with a half-open connection (Typically the client sends a SYN-ACK-ACK to complete the three way handshake). Half open connections consume resources eventually degrading the performance of the server.

   CISCO routers employ ‘TCP Intercept’ and ‘CAR – Committed Access Rate’ features to combat SYN-FLOOD. You can also change the default setting for the ‘maximum number of half-open TCP connections’

2. UDP Flood
   

   Here the server is flooded with UDP requests, degrading the performance of the Server

3. ICMP Flood
   

   Here the Server is flooded with ‘echo’ requests (which is an ICMP request), degrading the performance of the Server.

   It is best to drop ICMP packets at the router or Firewall.

4. Smurf
   

   Here the attacker sends ICMP request packets to the broadcast address of the target network using a spoofed source address. The target responds with a echo request to all the hosts in the network, eventually overwhelming the network.

5. Fraggle
   

   A flavor of Smurf attack which uses UDP Echo packets (UDP Port 7) instead of ICMP packets. Cisco routers can be configured to disable the TCP and UDP services (TCP and UDP small servers) to defend against Fraggle

6. Bluejacking and bluesnarfing
   

   Here the Bluetooth enabled devices are attached. In Bluejacking, unsolicited messages are sent. In Bluesnarfing, personal information such as pictures and contacts, and cell phone information such as serial numbers are stolen.

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Wired Equivalent Privacy:

The intention of WEP (Wired Equivalent Privacy) was to provide the same level of security as in Wired Networks. But it fell short greatly.

WEP uses 128bit key (with 24 bit initialization vector) which is very easy to crack. It uses RC4 (Rivest Cipher 4) stream cipher.

Two modes:

Open Systems Authentication:

No need of credentials from the client. After the initial association with AP (Access Point), WEP encrypts the whole conversation.

Shared Key Authentication:

Requires Client to present credentials to connect to AP before the encryption beings.

WEP can be enhanced by using ssh or tunneling.

WiFi Protected Access (WPA and WPA2):

WPA uses TKIP(Temporal Key Integrity Protocol), a sequence counter to prevent replay attacks and a 64 bit message integrity check. It combines a secret root key with initialization vector.

WPA2 uses AES with Cipher Block chaining message Authentication code Protocol (CCMP).

Both WPA and WPA supports several EAP extensions such as EAP-TLS, EAP-TTLS (Tunneled Transport Layer Security) and Protected EPA (PEAPv0,v1)

Commonly used VPN security technologies are:

1. Point to Point Tunneling Protocol (PPTP)
2. Layer2 Forwarding Protocol (L2F)
3. Layer2 Tunneling Protocol (L2TP)
4. IPSec
5. SSL

Point to Point Tunneling Protocol (PPTP):

1. Uses PAP, CHAP, EAP
2. Typically used in dial-up connections in Windows platform
3. Operates at Data Link Layer

Layer 2 forwarding Protocol (L2F):

1. Developed by CISCO
2. Similar to PPTP
3. Operates at Data Link Layer

Layer 2 tunneling Protocol (L2TP)

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There are 5 major remote access security technologies

1. RAS (Remote Access Service)
2. Radius
3. Diameter
4. TACACS

RAS (Remote Access Service):
Uses PPP (Point to Point Protocol) to secure dial-in, ISDN and serial links. Uses the following authentication mechanisms.

PAP (Password Authentication Protocol):

1. Two way hand shake
2. Sends passwords in clear text
3. No protection against replay or brute force attacks

CHAP (Challenge Handshake Protocol):

1. Uses three way hand shake
2. Both server and client need to have a shared secret preconfigured
3. Shared secret is stored in clear text. MS-CHAP allows the shared secret to be stored in encrypted form

EAP (Extensible Authentication Protocol):

1. Used primarily in Wireless networks
2. Supports various authentication mechanisms like MD5-Challenge, S/Key, generic token card and digital Certificates

1. Open-Source UDP based.
2. Provides authentication and accountability
3. Use provides username/password to a RADIUS client using PAP or CHAP. Radius client encrypts password and sends to RADIUS Server for authentication

1. Improved version of RADIUS
2. Uses TCP. Supports IPSsec, TLS

1. Uses UDP. Provides Authentication, Authorization and Accountability
2. XTACACS is an improved version but no longer used
3. TACACS+ is the current version. Supports several authentication mechanisms – PAP,CHAP,MS-CHAP,EAP,KERBEROS,Token Cards

Classifications of Firewalls:

1. Packet Filtering
2. Circuit Level Gateway
3. Application Level Gateway

Architectures of Firewall:

1. Screening Router
2. Dual Homed Gateway
3. Screened-Host Gateway
4. Screened Subnet

Here are the protocols commonly used in higher levels (5,6,7 of the OSI model)

Layer 5 (Session):

1. NetBIOS
2. NFS
3. RPC
4. SSH
5. SIP

Layer 6: (Presentation):

1. ASCII
2. ENCDIC
3. MPEG
4. JPG
5. GIF

Layer 7 (Application):

1. FTP,TFTP
2. SNMP
3. SMTP
4. MIME, S/MIME
5. HTTP,HTTPS,S-HTTP
6. POP3,IMAP
7. PEM
8. TELNET
9. S-RPC

IP (Internet protocol) is a Network Layer protocol (Layer 3) that considered ‘routed’ protocol. It addresses the Network Packets so that routing protocols like OSPF,BGP and RIP can correctly route the packet.

IP defines the IP addresses. IP address is a 32 bit number (4 octets). It comprises of Network and Host numbers. The higher order bits define the Network number as shown below.

There are 5 classes of IP addresses: