Trap Doors And Trojan Horses Essay

The Wooden Horse

The war between the Greeks and the Trojans is in its tenth year. The Trojans rejoice when the Greek army departs leaving behind a giant wooden horse. The Trojans are divided - should they set fire to the statue or should they worship it?

The story is mentioned in Homer's Odyssey, an epic poem about the Greek hero, Odysseus. It is told in more detail by the Roman poet, Virgil, in Book II of the Aeneid.

The most famous line from Virgil's version has an anti-Greek feel to it: "I fear the Greeks, especially when they are bringing gifts."

One of the most famous tricks in all literature is the subject of this, the third story in our Troy series (filed under Greek Myths)

Read by Natasha.
Proofread by Claire Deakin.
Duration 12 Minutes.


The happiest day in the history of Troy was when the Greek army sailed away. For ten long years the war had raged, and many of the finest and bravest warriors on both sides had fallen in battle. How the Trojans rejoiced as they walked along the shore where the Greek enemy had camped! Here, cruel Achilles had set up his tent. There, the arrogant King Agamemnon had commanded his men. Now, for the first time in their lives, the children of Troy could run and play in the foam of the sea, and teenage boys and girls could walk hand in hand beneath the cliffs.

Little did they realise that the enemy army had not set sail for far away Greece. Instead, they had only taken their ships to the other side of the island, called Tenedos; and there they were lurking, out of sight, but still not far away. It was all a cunning trick thought up by the wiliest of the Greeks, the red haired Odysseus (ode-iss-see-us), who was never short of a plan.

The Trojans saw that the Greeks had left behind a strange offering. It was a giant wooden horse with ribs made from the planks of fir trees. The people marvelled at the massive statue, but there were different opinions about what they should do with it. Some wise old men saw there was something not quite right about the horse, and advised that they should set fire to it straight away. Others warned that , the gods would be angry with them if they did not honour the statue. After all, the wooden horse was dedicated to grey-eyed Athena, the great goddess of wisdom, and nobody wanted to feel her wrath.

The crowd was wavering, and a white-bearded old Priest spoke out above the murmur. “Fellow citizens. Whatever this strange horse may be, remember this: it is always wise to fear the Greeks, especially when they are bringing gifts. By the great god Poseidon, Lord of the Seas, and by everything that is sacred, let us not fall into this deadly trap, for that is what it surely is!”

So saying, the old priest hurled a mighty spear at the horse, and it flew into the beast’s side and quivered, and the guts of the horse reverberated with an eerie hollow sound like a long, deep moan. Had the Trojans decided there and then to set fire to that horse of death, their lovely city would be standing to this day, and the descendants of King Priam would be living in peace and happiness.

Just then, a Trojan patrol came upon the scene, and they brought with them a prisoner – a Greek called Sinon whom the army had left behind.

“Now we will find out the truth!” said the Trojan guards, “Let’s poke this wretched Greek spy with our bronze spears until he tells us what this Greek gift is all about!”

When he heard this, the poor prisoner cried out: “No, please! Don’t harm me. I’ll happily tell you all you want to know - for cruel, scheming Odysseus is no more a friend of mine than he is of you.” - and so the Trojans listened to what Sinon had to say, and they tried to fathom whether or not he spoke the truth.

“Do you not think that the Greeks would have gladly given up this war before ten long years had passed? Let me tell you that many times they planned to leave their sufferings behind, as they have done now... But each time they prepared to sail away in their beaked black ships, the sea god Poseidon sent a terrible storm, and whipped up giant waves on the wine dark sea. They consulted a priest who told them the reason why the gods were inflicting such pain. You see, before he left his home in Argos, King Agamemnon, the great leader of men, waited an entire month for a wind to blow his ships to Troy. Eventually, he decided that the gods required a very special offering. And as usual, it was scheming Odysseus who thought up the plan. He sent for Agamemnon’s own daughter, his darling Iphigenia, and told her that she was to marry swift-footed Achilles. She came with great joy and gladness in her heart - for Achilles was the handsomest and bravest of the Greeks, but it was all a most dreadful trick. Instead of marrying Achilles at the altar on the cliffs high up above the sea, the priest sacrificed the lovely white-skinned young maiden to the sea god. Straight away, as the foul deed was done, the winds began to blow."

“Now, ten long years later, as we were waiting for a wind to take us back home, Odysseus came up with another plan. “I know,” he said, “Let’s sacrifice the most useless of those among us. Nobody will miss Sinon. He has only ever criticised our plans, and called us leaders wicked and foolish. We once sacrificed an innocent young girl, now let’s give the gods the life of a man, and you’ll see, they will send us a fair wind to blow us swiftly home.”

“But before Odysseus sent his guards to fetch me to my death, a rumour reached me of what he had said, and I ran into the woods and hid. So the Greeks came up with a second plan to appease the gods - and you see the result before you. This magnificent wooden horse is their offering, to say how sorry they are for all the needless death and destruction they have caused. Only bring it inside your walls before night falls because unless I am far wrong, there will be gold and treasure hidden deep inside the belly of that wooden horse.”

When the Trojans had heard Sinon’s tale, many of them were greedy for treasure, and they believed his wicked lies – for he spoke most convincingly but still the crowd was uncertain what to do – until that is, a most terrible thing happened. The
old priest who had thrown his spear at the horse was standing by the sea, when a great monster came swimming into shore and carried him off its jaws. It all happened in a flash, and the Trojans were filled with a strange terror.

Sinon one again called out: “You see, Trojans. Nothing but the truth I spoke! The Gods have rightly punished that wicked old priest for sending his spear into the wooden horse!" And now nobody dared to disagree.

The Trojans brought ropes and placed wheels beneath the statue’s feet, so that they might pull the wooden horse through the gates of their magnificent city. As the ill-omened procession entered Troy, girls and boys danced around the horse singing holy chants. There was rejoicing in the city, and even the fortune teller, Casandra, did not dare open her lips though she foresaw the imminent doom - for the gods had given Casandra the gift of clear-sighted prophecy but had decreed that not one person would believe her.

It was a clear moonlit night, and the Trojans carried on partying. Sinon the Greek had been set free, and nobody noticed that he lit a fire on the beach to signal to the army on the island of Tenedos that the wooden horse was within the walls of Troy. Next, he returned to the city and opened a secret door in the belly of the horse, and the Greek band of warriors, who had been hiding all that time within, let down a long rope- and they were led to the ground by wily Odysseus, who was the first of them to stand in the central square of magnificent Troy.

It was not long before the Greek intruders had surprised the guards on the main gates and killed them. Soon the wide doors were open, and the Greek army was surging into Troy. The Trojans were either drunk or sleeping and in no way ready to fight. On every side the city was in turmoil. Soon the palace of King Priam was in the grip of fire, and Helen – the most beautiful woman in the world, for whom these ten years of war had been fought, was throwing herself at the feet of her
Greek husband, King Menelaus, and protesting how she had been kidnapped and brought to Troy against her will. It was all lies, of course, but Menelaus was ready to be believe his lovely wife and took her once more in his arms.

Security Laboratory: Methods of Attack Series

These papers introduce you to the most common attack methods against computer systems and networks and the basic strategies used to mitigate those threats.

Other Related Articles in Security Laboratory: Methods of Attack Series


Logic Bombs, Trojan Horses, and Trap Doors


By Stephen Northcutt


There are many types of malicious code in the wild today. Though they are only a small subset of these, logic bombs, Trojan horses, and trap doors are fairly common.

Logic Bombs
Logic bombs are small programs or sections of a program triggered by some event such as a certain date or time, a certain percentage of disk space filled, the removal of a file, and so on. For example, a programmer could establish a logic bomb to delete critical sections of code if she is terminated from the company. Logic bombs are most commonly installed by insiders with access to the system.

UBS PaineWebber system administrator Roger Duronio has been charged with Logic bomb
Former UBS PaineWebber system administrator, Roger Duronio, has been charged with sabotaging company computer systems in an attempt to manipulate its stock price. Duronio placed logic bombs that deleted files on the computers. Duronio has been charged with one count of securities fraud and one count of violation of the Computer Fraud and Abuse Act.

Trojan Horses
Trojan horses (often just called Trojans) are programs that must be installed or executed by a user to be effective. Often, these are disguised as helpful or entertaining programs which can include operating system patches, Linux packages, or games. Once executed, however, Trojans perform actions the user did not intend such as opening certain ports for later intruder access, replacing certain files with other malicious files, and so on.1

"Assistant U.S. Attorney Mauro Wolfe gave his closing arguments to the jury in U.S. District Court here for more than two hours Monday. He told jurors that Roger Duronio, the defendant in this computer sabotage case, was the man with the motive, the means and the ability to do the crime. And on top of that, copies of the trigger for the logic bomb were found in his home."2 He was sentenced for 8 years.3

Roger Duronio showed all the classic signs of entitlement
Entitlement, railing at a perceived injustice, is known as a "trigger". A trigger, commonly seen in insider attack and espionage cases, is an event that causes an individual to choose to act out betrayal. "Many people, perhaps most people, experience some form of stress that threatens their self-image at some time in their lives. They face serious financial problems combined with an available opportunity for illegal gain; failure to compete effectively with their peers; perceived injustice at the hands of an employer or supervisor; termination from a job under circumstances that prompt resentment; rejection or betrayal by a spouse or other close family member."4

A chilling piece of journalism from Information Week shows this was quite likely to come.

"Wolfe reminded the jury about the testimony of Rajeev Khanna, manager for UBS's Unix Systems Group, at the time of the attack. Khanna had told the jury that Duronio went to him in 2000, saying he had "cash flow problems" and asking for a pay increase. Khanna said he had liked Duronio and went to bat for him, even though it was midyear and an unusual time to ask for, or give out, a pay raise. Khanna got Duronio a $10,000 bump in salary. But Wolfe was quick Monday to remind the jury that Duronio had not been satisfied with it. "It wasn't good enough," Wolfe told the jury. "The seeds were planted. He wasn't happy with what he was taking home."5

NOTE: This was such a serious breach of faith that Paine Webber changed their name to UBS Wealth Management after the incident.

Logic bombs for good

Some of these techniques can also be used against attackers in a devious sort of way. Administrators sometimes intentionally deploy pseudo flaws, also known as honey tokens, which are things that look vulnerable to attack but really act as alarms or triggers of automatic actions when an intruder attempts to exploit the flaw. Do not confuse the single pseudo flaw with the concept of a pseudo flaw that extends to encompass an entire host or network - often referred to as a honeypot or a honeynet; neither of these terms properly refers to a single pseudo flaw.

Trap doors
Trap doors, also referred to as backdoors, are bits of code embedded in programs by the programmer(s) to quickly gain access at a later time, often during the testing or debugging phase. If an unscrupulous programmer purposely leaves this code in or simply forgets to remove it, a potential security hole is introduced. Hackers often plant a backdoor on previously compromised systems to gain later access. Trap doors can be almost impossible to remove in a reliable manner. Often, reformatting the system is the only sure way.

DEBUG mode Sendmail, the most famous Unix Trap Door

The so called Morris worm took advantage of a common trap door in 1988. Here is a part of that famous account,

"Sendmail is the program that provides the SMTP mail service on TCP networks for Berkeley UNIX systems. It uses a simple character-oriented protocol to accept mail from remote sites. One feature of sendmail is that it permits mail to be delivered to processes instead of mailbox files; this can be used with (say) the vacation program to notify senders that you are out of town and are temporarily unable to respond to their mail. Normally this feature is only available to recipients. Unfortunately a little loophole was accidentally created when a couple of earlier security bugs were being fixed - if sendmail is compiled with the DEBUG flag, and the sender at runtime asks that sendmail enter debug mode by sending the debug command, it permits senders to pass in a command sequence instead of a user name for a recipient. Alas, most versions of sendmail are compiled with DEBUG, including the one that Sun sends out in its binary distribution. The worm mimics a remote SMTP connection, feeding in /dev/null as the name of the sender and a carefully crafted string as the recipient. The string sets up a command that deletes the header of the message and passes the body to a command interpreter. The body contains a copy of the worm bootstrap source plus commands to compile and run it. After the worm finishes the protocol and closes the connection to sendmail, the bootstrap will be built on the remote host and the local worm waits for its connection so that it can complete the process of building a new worm."6

The ultimate Trap Door, in the compiler itself
"Ken Thompson's Reflections on Trusting Trust7was the first major paper to describe black box backdoor issues, and points out that trust is relative. It described a very clever backdoor mechanism based upon the fact that people only review source (human-written) code, and not compiled machine code. A program called a compiler is used to create the second from the first, and the compiler is usually trusted to do an honest job.

Thompson's paper described a modified version of the Unix C compiler that would:
  • Put an invisible backdoor in the Unix login command when compiled and as a twist
  • Also add this feature undetectably to future compiler versions upon their compilation as well.
Because the compiler itself was a compiled program, users would be extremely unlikely to notice the machine code instructions that performed these tasks. (Because of the second task, the compiler's source code would appear "clean".) What's worse, in Thompson's proof of concept implementation, the subverted compiler also subverted the analysis program (the disassembler), so that anyone who examined the binaries in the usual way would not actually see the real code that was running, but something else instead. This version was never released into the wild. It was released to a sibling Bell Labs organization as a test case; they never found the attack."8

Defending against logic bombs and trap/back doors
According the the Chey Cobb blog,

"How can companies defend against such attacks? Some executives may bridle at our answer, but we think it is the right one: by hiring the right people and then treating them right. In other words, this is a people problem and so it needs a human solution. All the technology in the world is not going to prevent an insider, with authorized system access and detailed knowledge of the system, from planting a logic bomb. There are some technologies, such as network surveillance and monitoring programs, that might detect attempts to create logic bombs. Integrity checking software might deflect attacks from logic bombs. Properly enforced software development policies and procedures will make it harder for someone to plant a logic bomb. But the bottom line is that a determined insider is almost impossible to stop."9

Indeed it is a tough problem. In the case of Roger Duronio, it is not clear if more money would have helped him despite the fact that he had a supportive supervisor. Of the five types of defense in depth architectures, the hardest to implement, threat vector analysis10, works best against this difficult issue. We have little doubt at this point that UBS Wealth Management has a documented threat of unauthorized modification of code and has determined the vectors that one would have to use to accomplish this. Generally this requires separation of duties so that one person cannot move modified code to a production system; they can, at most, move it to a staging area. In addition, we would not be surprised to find code audits high on the list!

SANS courses that teach how to defend against logic bombs and trap doors include:


1 http://www.informationweek.com/story/showArticle.jhtml?articleID=188700855
2 http://www.darkreading.com/document.asp?doc_id=98858
3 http://www.theregister.co.uk/2006/12/13/ubs_logic_bomber_sentenced/
4 http://rf-web.tamu.edu/security/secguide/Treason/Insider.htm
5 http://www.informationweek.com/news/showArticle.jhtml?articleID=190301972
6 http://www.google.com/search?q=cache:cihLehcH3WMJ:ftp.cerias.purdue.edu/pub/doc/morris_worm/seely.PS.Z
7 http://www.acm.org/classics/sep95/
8 http://en.wikipedia.org/wiki/Backdoor
9 http://www.cheycobb.com/logic_bombs.html
10 http://www.sans.edu/resources/securitylab/316.php
11 http://www.sans.org/training/description.php?tid=390
12 http://www.sans.org/training/description.php?tid=447

Other Related Articles in Security Laboratory: Methods of Attack Series

  • Logic Bombs, Trojan Horses, and Trap Doors - May 2nd, 2007

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