200-201 Network Intrusion Analysis Practice Question
An analyst is reviewing PCAP and sees a TCP stream with a Wireshark filter 'tcp.stream eq 0'. The conversation shows an interactive shell session with commands like 'whoami' and 'ls'. This is most likely evidence of what?
⚠ Common exam trap
Watch out — candidates often confuse an interactive shell session with other types of attacks that also involve network traffic, such as DNS tunneling or SQL injection, because candidates may not recognize the specific commands and the nature of a reverse shell.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Reverse shell
The PCAP shows an interactive shell session with commands like 'whoami' and 'ls' over TCP. This is characteristic of a reverse shell, where an attacker compromises a host and establishes a command-and-control channel back to their machine, allowing interactive command execution. The use of 'tcp.stream eq 0' in Wireshark simply isolates a specific TCP conversation, and the presence of shell commands confirms a reverse shell.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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DNS tunneling
Why it's wrong here
DNS tunneling uses DNS protocol.
- ✓
Reverse shell
Why this is correct
An interactive shell where the remote host executes commands such as whoami and ls indicates the attacker's machine is receiving a session from the victim, the defining pattern of a reverse shell. The victim initiated the outbound connection, evading inbound firewall rules.
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SQL injection
Why it's wrong here
SQL injection appears as malformed SQL statements or database error responses within HTTP traffic, not an interactive shell with whoami and ls commands. It is tempting because both are web-borne attacks, but SQL injection would be the right classification when the stream shows database query manipulation rather than remote command execution.
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ARP spoofing
Why it's wrong here
ARP spoofing is a layer 2 attack visible as duplicate or conflicting ARP replies mapping one IP to multiple MAC addresses, not an interactive shell. It is tempting because it enables man-in-the-middle interception, but ARP spoofing would be correct when the capture shows forged ARP traffic rather than shell commands.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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