TY - CHAP A1 - Mayer, Peter A1 - Poddebniak, Damian A1 - Fischer, Konstantin A1 - Brinkmann, Marcus A1 - Somorovsky, Juraj A1 - Schinzel, Sebastian A1 - Volkamer, Melanie T1 - "I don’t know why I check this...'' - Investigating Expert Users' Strategies to Detect Email Signature Spoofing Attacks T2 - Eighteenth Symposium on Usable Privacy and Security (SOUPS 2022) N2 - OpenPGP is one of the two major standards for end-to-end email security. Several studies showed that serious usability issues exist with tools implementing this standard. However, a widespread assumption is that expert users can handle these tools and detect signature spoofing attacks. We present a user study investigating expert users' strategies to detect signature spoofing attacks in Thunderbird. We observed 25 expert users while they classified eight emails as either having a legitimate signature or not. Studying expert users explicitly gives us an upper bound of attack detection rates of all users dealing with PGP signatures. 52% of participants fell for at least one out of four signature spoofing attacks. Overall, participants did not have an established strategy for evaluating email signature legitimacy. We observed our participants apply 23 different types of checks when inspecting signed emails, but only 8 of these checks tended to be useful in identifying the spoofed or invalid signatures. In performing their checks, participants were frequently startled, confused, or annoyed with the user interface, which they found supported them little. All these results paint a clear picture: Even expert users struggle to verify email signatures, usability issues in email security are not limited to novice users, and developers may need proper guidance on implementing email signature GUIs correctly. Y1 - 2022 UR - https://www.usenix.org/conference/soups2022/presentation/mayer SN - 978-1-939133-30-4 SP - 77 EP - 96 PB - USENIX Association CY - Boston, MA ER - TY - JOUR A1 - Brinkmann, Marcus A1 - Dresen, Christian A1 - Merget, Robert A1 - Poddebniak, Damian A1 - Müller, Jens A1 - Somorovsky, Juraj A1 - Schwenk, Jörg A1 - Schinzel, Sebastian T1 - ALPACA: Application Layer Protocol Confusion - Analyzing and Mitigating Cracks in TLS Authentication JF - 30th USENIX Security Symposium Y1 - 2021 UR - https://www.usenix.org/conference/usenixsecurity21/presentation/brinkmann ER - TY - CHAP A1 - Schinzel, Sebastian T1 - An Efficient Mitigation Method for Timing Side Channels on the Web T2 - 2nd International Workshop on Constructive Side-Channel Analysis and Secure Design (COSADE 2011) Y1 - 2011 ER - TY - CHAP A1 - Gierling, Markus A1 - Dresen, Christian A1 - Eich, Hans A1 - Mittman, Karin A1 - Schinzel, Sebastian A1 - Haverkamp, Uwe T1 - Analysis and consequences of an imaging process concerning the cyber security of a networked computer tomography scanner T2 - STRAHLENTHERAPIE UND ONKOLOGIE KW - Cyber Security KW - networked computer tomography scanner Y1 - 2018 SP - 185 EP - 186 ER - TY - CHAP A1 - Willing, Markus A1 - Dresen, Christian A1 - Haverkamp, Uwe A1 - Schinzel, Sebastian T1 - Analyzing medical device connectivity and its effect on cyber security in german hospitals N2 - Background: Modern healthcare devices can be connected to computer networks and many western healthcareinstitutions run those devices in networks. At the same time, cyber attacks are on the rise and there is evidence thatcybercriminals do not spare critical infrastructure such as major hospitals, even if they endanger patients. Intuitively,the more and closer connected healthcare devices are to public networks, the higher the risk of getting attacked. Methods: To asses the current connectivity status of healthcare devices, we surveyed the field of German hospitalsand especially University Medical Center UMCs. Results: The results show a strong correlation between the networking degree and the number of medical devices.The average number of medical devices is 25.150, with a median of networked medical devices of 3.600. Actual keyusers of networked medical devices are the departments Radiology, Intensive Care, Radio-Oncology RO, NuclearMedicine NUC, and Anaesthesiology in the group of UMCs. In the next five years, the usage of networked medicaldevices will increase significantly in the departments of Surgery, Intensive Care, and Radiology. We detected a strongcorrelation between the degree of connectivity and the likelihood of being attacked.The survey answers regarding the cyber security status reveal a lack of security basics in some of the inquiredhospitals. We did discover successful attacks in hospitals with separated or subsidiary departments. A fusion ofcompetencies on an organizational level facilitates the right behavior here. Most hospitals rated themselvespredominantly positively in the self-assessment but also stated the usefulness of IT security insurance.Conclusions:Concluding our results, hospitals are already facing the consequences of omitted measures within theirgrowing pool of medical devices. Continuously relying on historically grown structures without adaption and trustingmanufactures to solve vectors is a critical behavior that could seriously endanger patients. Y1 - 2020 U6 - http://dx.doi.org/10.1186/s12911-020-01259-y PB - BMC Medical Informatics and Decision Making volume ER - TY - CHAP A1 - Poddebniak, Damian A1 - Somorovsky, Juraj A1 - Schinzel, Sebastian A1 - Lochter, Manfred A1 - Rösler, Paul T1 - Attacking Deterministic Signature Schemes using Fault Attacks T2 - 3rd IEEE European Symposium on Security and Privacy Y1 - 2018 ER - TY - JOUR A1 - Willing, Markus A1 - Dresen, Christian A1 - Gerlitz, Eva A1 - Haering, Maximilian A1 - Smith, Matthew A1 - Binnewies, Carmen A1 - Guess, Tim A1 - Haverkamp, Uwe A1 - Schinzel, Sebastian T1 - Behavioral responses to a cyber attack in a hospital environment JF - Nature -- Scientific Reports N2 - Technical and organizational steps are necessary to mitigate cyber threats and reduce risks. Human behavior is the last line of defense for many hospitals and is considered as equally important as technical security. Medical staff must be properly trained to perform such procedures. This paper presents the first qualitative, interdisciplinary research on how members of an intermediate care unit react to a cyberattack against their patient monitoring equipment. We conducted a simulation in a hospital training environment with 20 intensive care nurses. By the end of the experiment, 12 of the 20 participants realized the monitors’ incorrect behavior. We present a qualitative behavior analysis of high performing participants (HPP) and low performing participants (LPP). The HPP showed fewer signs of stress, were easier on their colleagues, and used analog systems more often than the LPP. With 40% of our participants not recognizing the attack, we see room for improvements through the use of proper tools and provision of adequate training to prepare staff for potential attacks in the future. Y1 - 2021 U6 - http://dx.doi.org/10.1038/s41598-021-98576-7 ER - TY - CHAP A1 - Jager, Tibor A1 - Schinzel, Sebastian A1 - Somorovsky, Juraj T1 - Bleichenbacher's Attack Strinkes Again: Breaking PKCS#1 v1.5 in XML Encryption T2 - 17th European Symposium on Research in Computer Security (ESORCIS 2012) Y1 - 2012 ER - TY - CHAP A1 - Ising, Fabian A1 - Poddebniak, Damian A1 - Kappert, Tobias A1 - Saatjohann, Christoph A1 - Schinzel, Sebastian T1 - Content-Type: multipart/oracle -- Tapping into Format Oracles in Email End-to-End Encryption T2 - 32nd USENIX Security Symposium N2 - S/MIME and OpenPGP use cryptographic constructions repeatedly shown to be vulnerable to format oracle attacks in protocols like TLS, SSH, or IKE. However, format oracle attacks in the End-to-End Encryption (E2EE) email setting are considered impractical as victims would need to open many attacker-modified emails and communicate the decryption result to the attacker. But is this really the case? In this paper, we survey how an attacker may remotely learn the decryption state in email E2EE. We analyze the interplay of MIME and IMAP and describe side-channels emerging from network patterns that leak the decryption status in Mail User Agents (MUAs). Concretely, we introduce specific MIME trees that produce decryption-dependent net work patterns when opened in a victim’s email client. We survey 19 OpenPGP- and S/MIME-enabled email clients and four cryptographic libraries and uncover a side-channel leaking the decryption status of S/MIME messages in one client. Further, we discuss why the exploitation in the other clients is impractical and show that it is due to missing feature support and implementation quirks. These unintended defenses create an unfortunate conflict between usability and security. We present more rigid countermeasures for MUA developers and the standards to prevent exploitation. Y1 - 2023 UR - https://www.usenix.org/conference/usenixsecurity23 PB - USENIX Association ER - TY - CHAP A1 - Dresen, Christian A1 - Ising, Fabian A1 - Poddebniak, Damian A1 - Kappert, Tobias A1 - Holz, Thorsten A1 - Schinzel, Sebastian ED - Zhou, Jianying T1 - CORSICA: Cross-Origin Web Service Identification T2 - The 15th ACM ASIA Conference on Computer and Communications Security N2 - Vulnerabilities in private networks are difficult to detect for attackers outside of the network. While there are known methods for port scanning internal hosts that work by luring unwitting internal users to an external web page that hosts malicious JavaScript code, no such method for detailed and precise service identification is known. The reason is that the Same Origin Policy (SOP) prevents access to HTTP responses of other origins by default. We perform a structured analysis of loopholes in the SOP that can be used to identify web applications across network boundaries. For this, we analyze HTML5, CSS, and JavaScript features of standard-compliant web browsers that may leak sensitive information about cross-origin content. The results reveal several novel techniques, including leaking JavaScript function names or styles of cross-origin requests that are available in all common browsers. We implement and test these techniques in a tool called CORSICA. It can successfully identify 31 of 42 (74%) of web services running on different IoT devices as well as the version numbers of the four most widely used content management systems WordPress, Drupal, Joomla, and TYPO3. CORSICA can also determine the patch level on average down to three versions (WordPress), six versions (Drupal), two versions (Joomla), and four versions (TYPO3) with only ten requests on average. Furthermore, CORSICA is able to identify 48 WordPress plugins containing 65 vulnerabilities. Finally, we analyze mitigation strategies and show that the proposed but not yet implemented strategies Cross-Origin Resource Policy (CORP)} and Sec-Metadata would prevent our identification techniques. Y1 - 2020 UR - https://asiaccs2020.cs.nthu.edu.tw/program/ ER - TY - CHAP A1 - Freiling, Felix A1 - Schinzel, Sebastian T1 - Detecting Hidden Storage Side Channel Vulnerabilities in Networked Applications T2 - IFIP sec2011 - Future Challenges in Security and Privacy for Academia and Industry Y1 - 2011 SN - 978-3-642-21423-3 U6 - http://dx.doi.org/10.1007/978-3-642-21424-0_4 SP - 41 EP - 55 PB - Springer, Berlin, Heidelberg ET - Volume 354 ER - TY - CHAP A1 - Aviram, Nimrod A1 - Schinzel, Sebastian A1 - Somorovsky, Juraj A1 - Heninger, Nadia A1 - Dankel, Maik A1 - Steube, Jens A1 - Valenta, Luke A1 - Adrian, David A1 - Halderman, J. Alex A1 - Dukhovni, Viktor A1 - Käsper, Emilia A1 - Cohney, Shaanan A1 - Engels, Susanne A1 - Paar, Christof A1 - Shavitt, Yuval T1 - DROWN: Breaking TLS Using SSLv2 T2 - 25th Usenix Security Symposium Y1 - 2016 SP - 689 EP - 706 PB - Usenix Association. CY - Austin, TX. ER - TY - CHAP A1 - Poddebniak, Damian A1 - Dresen, Christian A1 - Müller, Jens A1 - Ising, Fabian A1 - Schinzel, Sebastian A1 - Friedberg, Simon A1 - Somorovsky, Juraj A1 - Schwenk, Jörg T1 - Efail: Breaking S/MIME and OpenPGP Email Encryption using Exfiltration Channels T2 - USENIX Security 2018 Y1 - 2018 SN - 978-1-931971-46-1 CY - Baltimore, MD, USA ET - 27th ER - TY - CHAP A1 - Willing, Markus A1 - Saatjohann, Christoph A1 - Rath, Benjamin A1 - Schinzel, Sebastian A1 - Eckardt, Lars A1 - Köbe, Julia T1 - Experiences with General Data Protection Regulations and Remote Monitoring of Implantable Rhythm Devices T2 - 87. Jahrestagung der Deutsche Gesellschaft für Kardiologie – Herz‑ und Kreislauforschung e.V Y1 - 2021 U6 - http://dx.doi.org/10.1007/s00392-021-01843-w PB - Springer-Verlag GmbH ER - TY - CHAP A1 - Bauer, Johannes A1 - Schinzel, Sebastian A1 - Felix, C. A1 - Freiling, Andreas T1 - Information leakage behind the curtain: Abusing anti-EMI features for covert communication T2 - Hardware Oriented Security and Trust (HOST), 2016 IEEE International Symposium on Y1 - 2016 U6 - http://dx.doi.org/10.1109/HST.2016.7495570 SP - 130 EP - 134 ER - TY - JOUR A1 - Schinzel, Sebastian A1 - Thünemann, Maximilian A1 - Löhr, Dennis T1 - Internetzensus - Das Internet scannen und auf Schwachstellen untersuchen JF - iX - Security kompakt Y1 - 2014 SN - 4018837005 IS - 4 ER - TY - CHAP A1 - Schumilo, Sergej A1 - Aschermann, Cornelius A1 - Gawlik, Robert A1 - Schinzel, Sebastian A1 - Holz, Thorsten T1 - kAFL: Hardware-Assisted Feedback Fuzzing for OS Kernels T2 - 26th Usenix Security Symposium Y1 - 2017 ER - TY - CHAP A1 - Müller, Jens A1 - Brinkmann, Marcus A1 - Poddebniak, Damian A1 - Schinzel, Sebastian A1 - Schwenk, Jörg T1 - Mailto: Me Your Secrets. On Bugs and Features in Email End-to-End Encryption T2 - 2020 IEEE Conference on Communications and Network Security (CNS) N2 - OpenPGP and S/MIME are the two major standards for email end-to-end encryption. We show practical attacks against both encryption schemes in the context of email. First, we present a design flaw in the key update mechanism, allowing a third party to deploy a new key to the communication partners. Second, we show how email clients can be tricked into acting as an oracle for decryption or signing by exploiting their functionality to auto-save drafts. Third, we demonstrate how to exfiltrate the private key, based on proprietary mailto parameters implemented by various email clients. An evaluation shows that 8 out of 20 tested email clients are vulnerable to at least one attack. While our attacks do not target the underlying cryptographic primitives, they raise concerns about the practical security of OpenPGP and S/MIME email applications. Finally, we propose countermeasures and discuss their advantages and disadvantages. KW - Cyber Security KW - PGP KW - S/MIME Y1 - 2020 U6 - http://dx.doi.org/10.1109/CNS48642.2020.9162218 SP - 1 EP - 9 ER - TY - CHAP A1 - Müller, Jens A1 - Ising, Fabian A1 - Mla­de­nov, Vla­dis­lav A1 - Mainka, Chris­ti­an A1 - Schinzel, Sebastian A1 - Schwenk, Jörg T1 - Of­fice Do­cu­ment Se­cu­ri­ty and Pri­va­cy T2 - 14th USE­NIX Work­shop on Of­fen­si­ve Tech­no­lo­gies (WOOT 2020) N2 - OOXML and ODF are the de facto standard data formats for word processing, spreadsheets, and presentations. Both are XML-based, feature-rich container formats dating back to the early 2000s. In this work, we present a systematic analysis of the capabilities of malicious office documents. Instead of focusing on implementation bugs, we abuse legitimate features of the OOXML and ODF specifications. We categorize our attacks into five classes: (1) Denial-of-Service attacks affecting the host on which the document is processed. (2) Invasion of privacy attacks that track the usage of the document. (3) Information disclosure attacks exfiltrating personal data out of the victim's computer. (4) Data manipulation on the victim's system. (5) Code execution on the victim's machine. We evaluated the reference implementations – Microsoft Office and LibreOffice – and found both of them to be vulnerable to each tested class of attacks. Finally, we propose mitigation strategies to counter these attacks. KW - Cyber Security KW - Open Document Format KW - docx Y1 - 2020 UR - https://www.usenix.org/conference/woot20/presentation/muller PB - USENIX ER - TY - CHAP A1 - Müller, Jens A1 - Ising, Fabian A1 - Mldadenov, Vladislav A1 - Mainka, Christian A1 - Schinzel, Sebastian A1 - Schwenk, Jörg T1 - Practical Decryption exFiltration: Breaking PDF Encryption T2 - The 26th ACM Conference on Computer and Communications, Security (CCS 2019), London, United Kingdom N2 - The Portable Document Format, better known as PDF, is one of themost widely used document formats worldwide, and in order to en-sure information confidentiality, this file format supports documentencryption. In this paper, we analyze PDF encryption and showtwo novel techniques for breaking the confidentiality of encrypteddocuments. First, we abuse the PDF feature ofpartially encrypteddocuments to wrap the encrypted part of the document withinattacker-controlled content and therefore, exfiltrate the plaintextonce the document is opened by a legitimate user. Second, we abusea flaw in the PDF encryption specification to arbitrarily manipulateencrypted content. The only requirement is that a single block ofknown plaintext is needed, and we show that this is fulfilled bydesign. Our attacks allow the recovery of the entire plaintext of en-crypted documents by using exfiltration channels which are basedon standard compliant PDF properties.We evaluated our attacks on 27 widely used PDF viewers andfound all of them to be vulnerable. We responsibly disclosed thevulnerabilities and supported the vendors in fixing the issue Y1 - 2019 UR - https://pdf-insecurity.org/download/paper-pdf_encryption-ccs2019.pdf U6 - http://dx.doi.org/10.1145/3319535.3354214 ER -